Ipsilateral and contralateral coadministration of influenza and COVID-19 vaccines produce similar antibody responses.

BACKGROUND: World Health Organisation (WHO) and USA Centers for Disease Control and Prevention (U.S. CDC) recommendations now allow simultaneous administration of COVID-19 and other vaccines. We compared antibody responses after coadministration of influenza and bivalent COVID-19 vaccines in the same (ipsilateral) arm vs. different (contralateral) arms. METHODS: Pre- and post-vaccination serum samples from individuals in the Prospective Assessment of COVID-19 in a Community (PACC) cohort were used to conduct haemaglutination inhibition (HI) assays with the viruses in the 2022-2023 seasonal influenza vaccine and focus reduction neutralisation tests (FRNT) using a BA.5 SARS-CoV-2 virus. The effect of ipsilateral vs. contralateral vaccination on immune responses was inferred in a model that accounted for higher variance in vaccine responses at lower pre-vaccination titers. FINDINGS: Ipsilateral vaccination did not cause higher influenza vaccine responses compared to contralateral vaccination. The response to SARS-CoV-2 was slightly increased in the ipsilateral group, but equivalence was not excluded. INTERPRETATION: Coadministration of influenza and bivalent COVID-19 vaccines in the same arm or different arms did not strongly influence the antibody response to either vaccine. FUNDING: This work was supported by the U.S. CDC (grant number: 75D30120C09259).

Post-recovery health domain scores among outpatients by SARS-CoV-2 testing status during the pre-Delta period.

BACKGROUND: Symptoms of COVID-19 including fatigue and dyspnea, may persist for weeks to months after SARS-CoV-2 infection. This study compared self-reported disability among SARS-CoV-2-positive and negative persons with mild to moderate COVID-19-like illness who presented for outpatient care before widespread COVID-19 vaccination. METHODS: Unvaccinated adults with COVID-19-like illness enrolled within 10 days of illness onset at three US Flu Vaccine Effectiveness Network sites were tested for SARS-CoV-2 by molecular assay. Enrollees completed an enrollment questionnaire and two follow-up surveys (7-24 days and 2-7 months after illness onset) online or by phone to assess illness characteristics and health status. The second follow-up survey included questions measuring global health, physical function, fatigue, and dyspnea. Scores in the four domains were compared by participants' SARS-CoV-2 test results in univariate analysis and multivariable Gamma regression. RESULTS: During September 22, 2020 - February 13, 2021, 2712 eligible adults were enrolled, 1541 completed the first follow-up survey, and 650 completed the second follow-up survey. SARS-CoV-2-positive participants were more likely to report fever at acute illness but were otherwise comparable to SARS-CoV-2-negative participants. At first follow-up, SARS-CoV-2-positive participants were less likely to have reported fully or mostly recovered from their illness compared to SARS-CoV-2-negative participants. At second follow-up, no differences by SARS-CoV-2 test results were detected in the four domains in the multivariable model. CONCLUSION: Self-reported disability was similar among outpatient SARS-CoV-2-positive and -negative adults 2-7 months after illness onset.

Anti-SARS-CoV-2 Antibody Levels Associated with COVID-19 Protection in Outpatients Tested for SARS-CoV-2, US Flu VE Network, October 2021-June 2022.

BACKGROUND: We assessed associations between binding antibody (bAb) concentration <5 days of symptom onset and testing positive for COVID-19 among patients in a test-negative study. METHODS: From October 2021─June 2022, study sites in seven states enrolled patients aged ≥6 months presenting with acute respiratory illness. Respiratory specimens were tested for SARS-CoV-2. In blood specimens, we measured concentrations of anti-SARS-CoV-2 antibodies against the ancestral strain spike protein receptor binding domain (RBD) and nucleocapsid (N) antigens in standardized binding antibody units (BAU/mL). Percent change in odds of COVID-19 by increasing anti-RBD bAb was estimated using logistic regression as (1-adjusted odds ratio of COVID-19)x100, adjusting for COVID-19 mRNA vaccine doses, age, site, and high-risk exposure. RESULTS: Out of 2,018 symptomatic patients, 662 (33%) tested positive for acute SARS-CoV-2 infection. Geometric mean RBD bAb were lower among COVID-19 cases than SARS-CoV-2 test-negative patients during both the Delta-predominant (112 vs. 498 BAU/mL) and Omicron-predominant (823 vs. 1,189 BAU/mL) periods. Acute phase ancestral spike RBD bAb associated with 50% lower odds of COVID-19 were 1,968 BAU/mL against Delta and 3,375 BAU/mL against Omicron; thresholds may differ in other laboratories. CONCLUSION: During acute illness, antibody concentrations against ancestral spike RBD were associated with protection against COVID-19.

Neutralizing Immunity Against Antigenically Advanced Omicron BA.5 in Children After SARS-CoV-2 Infection.

We assessed serum neutralization of Omicron BA.5 in children following SARS-CoV-2 infection during the Delta or Omicron BA.1/BA.2 variant period. Convalescent BA.5 titers were higher following infections during the Omicron BA.1/BA.2 vs Delta variant period, and in vaccinated vs unvaccinated children. Titers against BA.5 did not differ by age group.

Symptoms, viral loads, and rebound among COVID-19 outpatients treated with nirmatrelvir/ritonavir compared to propensity score matched untreated individuals.

BACKGROUND: Nirmatrelvir/ritonavir (N/R) reduces severe outcomes among patients with COVID-19; however, rebound after treatment has been reported. We compared symptom and viral dynamics in community-based individuals with COVID-19 who completed N/R and similar untreated individuals. METHODS: We identified symptomatic participants who tested SARS-CoV-2 positive and were N/R eligible from a COVID-19 household transmission study: index cases from ambulatory settings and their households were enrolled, collecting daily symptoms, medication use, and respiratory specimens for quantitative PCR for 10 days, March 2022-May 2023. Participants who completed N/R (treated) were propensity score matched to untreated participants. We compared symptom rebound, viral load (VL) rebound, average daily symptoms, and average daily VL by treatment status measured after N/R completion or, if untreated, seven days after symptom onset. RESULTS: Treated (n=130) and untreated participants (n=241) had similar baseline characteristics. After treatment completion, treated participants had greater occurrence of symptom rebound (32% vs 20%; p=0.009) and VL rebound (27% vs 7%; p<0.001). Average daily symptoms were lower among treated participants compared to untreated participants without symptom rebound (1.0 vs 1.6; p<0.01), but not statistically lower with symptom rebound (3.0 vs 3.4; p=0.5). Treated participants had lower average daily VLs without VL rebound (0.9 vs 2.6; p<0.01), but not statistically lower with VL rebound (4.8 vs 5.1; p=0.7). CONCLUSIONS: Individuals who completed N/R experienced fewer symptoms and lower VL but were more likely to have rebound compared to untreated individuals. Providers should still prescribe N/R, when indicated, and communicate possible increased rebound risk to patients.

Antibody response to symptomatic infection with SARS-CoV-2 Omicron variant viruses, December 2021-June 2022.

To describe humoral immune responses to symptomatic SARS-CoV-2 infection, we assessed immunoglobulin G binding antibody levels using a commercial multiplex bead assay against SARS-CoV-2 ancestral spike protein receptor binding domain (RBD) and nucleocapsid protein (N). We measured binding antibody units per mL (BAU/mL) during acute illness within 5 days of illness onset and during convalescence in 105 ambulatory patients with laboratory-confirmed SARS-CoV-2 infection with Omicron variant viruses. Comparing acute- to convalescent phase antibody concentrations, geometric mean anti-N antibody concentrations increased 47-fold from 5.5 to 259 BAU/mL. Anti-RBD antibody concentrations increased 2.5-fold from 1258 to 3189 BAU/mL.

Influenza vaccination coverage among persons ages six months and older in the Vaccine Safety Datalink in the 2017-18 through 2022-23 influenza seasons.

BACKGROUND: In the United States, annual vaccination against seasonal influenza is recommended for all people ages ≥ 6 months. Vaccination coverage assessments can identify populations less protected from influenza morbidity and mortality and help to tailor vaccination efforts. Within the Vaccine Safety Datalink population ages ≥ 6 months, we report influenza vaccination coverage for the 2017-18 through 2022-23 seasons. METHODS: Across eight health systems, we identified influenza vaccines administered from August 1 through March 31 for each season using electronic health records linked to immunization registries. Crude vaccination coverage was described for each season, overall and by self-reported sex; age group; self-reported race and ethnicity; and number of separate categories of diagnoses associated with increased risk of severe illness and complications from influenza (hereafter referred to as high-risk conditions). High-risk conditions were assessed using ICD-10-CM diagnosis codes assigned in the year preceding each influenza season. RESULTS: Among individual cohorts of more than 12 million individuals each season, overall influenza vaccination coverage increased from 41.9 % in the 2017-18 season to a peak of 46.2 % in 2019-20, prior to declaration of the COVID-19 pandemic. Coverage declined over the next three seasons, coincident with widespread SARS-CoV-2 circulation, to a low of 40.3 % in the 2022-23 season. In each of the six seasons, coverage was lowest among males, 18-49-year-olds, non-Hispanic Black people, and those with no high-risk conditions. While decreases in coverage were present in all age groups, the declines were most substantial among children: 2022-23 season coverage for children ages six months through 8 years and 9-17 years was 24.5 % and 22.4 % (14 and 10 absolute percentage points), respectively, less than peak coverage achieved in the 2019-20 season. CONCLUSIONS: Crude influenza vaccination coverage increased from 2017 to 18 through 2019-20, then decreased to the lowest level in the 2022-23 season. In this insured population, we identified persistent disparities in influenza vaccination coverage by sex, age, and race and ethnicity. The overall low coverage, disparities in coverage, and recent decreases in coverage are significant public health concerns.

COVID-19 Booster Dose Reminder/Recall for Adolescents: Findings From a Health-Care System in Wisconsin.

PURPOSE: This study assessed efficacy of one-time COVID-19 booster reminder/recall for booster eligible adolescents in a health-care system in Wisconsin. METHODS: COVID-19 booster eligible patients aged 12-17 years were randomized 1:1 to receive one reminder/recall message from the health-care system using the parent's preferred communication method (intervention) or no reminder/recall (usual care) in May 2022. RESULTS: Reminder/recall was sent to 2,146/4,296 (50%) adolescent patients. During the 90-day evaluation period following randomization, booster dose receipt was 2.0 percentage points (CI: 0.3%-3.7%) higher in the intervention (10.0%) versus usual care groups (8.0%). Among patients with ≥1 preventive visit during the evaluation period, uptake was 7.5 percentage points higher in the intervention (16.4%) versus usual care groups (8.9%). DISCUSSION: A single COVID-19 booster dose reminder/recall resulted in a small but statistically significant increase in booster dose receipt, though uptake overall was low. Additional strategies are needed to increase uptake.

Influenza Vaccination Among Pregnant People Before and During the Coronavirus Disease 2019 (COVID-19) Pandemic.

There are limited data on influenza vaccination coverage among pregnant people in the United States during the coronavirus disease 2019 (COVID-19) pandemic. Within the Vaccine Safety Datalink, we conducted a retrospective cohort study to examine influenza vaccination coverage during the 2016-2017 through the 2021-2022 influenza seasons among pregnant people aged 18-49 years. Using influenza vaccines administered through March each season, we assessed crude coverage by demographic and clinical characteristics. Annual influenza vaccination coverage increased from the 2016-2017 season (63.0%) to a high of 71.0% in the 2019-2020 season. After the start of the COVID-19 pandemic, it decreased to a low of 56.4% (2021-2022). In each of the six seasons, coverage was lowest among pregnant people aged 18-24 years and among non-Hispanic Black pregnant people. The 2021-2022 season had the lowest coverage across all age and race and ethnicity groups. The recent decreases highlight the need for continued efforts to improve coverage among pregnant people.

Prior SARS-CoV-2 infection and COVID-19 vaccine effectiveness against outpatient illness during widespread circulation of SARS-CoV-2 Omicron variant, US Flu VE network.

BACKGROUND: We estimated combined protection conferred by prior SARS-CoV-2 infection and COVID-19 vaccination against COVID-19-associated acute respiratory illness (ARI). METHODS: During SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variant circulation between October 2021 and April 2022, prospectively enrolled adult patients with outpatient ARI had respiratory and filter paper blood specimens collected for SARS-CoV-2 molecular testing and serology. Dried blood spots were tested for immunoglobulin-G antibodies against SARS-CoV-2 nucleocapsid (NP) and spike protein receptor binding domain antigen using a validated multiplex bead assay. Evidence of prior SARS-CoV-2 infection also included documented or self-reported laboratory-confirmed COVID-19. We used documented COVID-19 vaccination status to estimate vaccine effectiveness (VE) by multivariable logistic regression by prior infection status. RESULTS: Four hundred fifty-five (29%) of 1577 participants tested positive for SARS-CoV-2 infection at enrollment; 209 (46%) case-patients and 637 (57%) test-negative patients were NP seropositive, had documented previous laboratory-confirmed COVID-19, or self-reported prior infection. Among previously uninfected patients, three-dose VE was 97% (95% confidence interval [CI], 60%-99%) against Delta, but not statistically significant against Omicron. Among previously infected patients, three-dose VE was 57% (CI, 20%-76%) against Omicron; VE against Delta could not be estimated. CONCLUSIONS: Three mRNA COVID-19 vaccine doses provided additional protection against SARS-CoV-2 Omicron variant-associated illness among previously infected participants.

Effectiveness of first and second COVID-19 mRNA vaccine monovalent booster doses during a period of circulation of Omicron variant sublineages: December 2021-July 2022.

Background: US recommendations for COVID-19 vaccine boosters have expanded in terms of age groups covered and numbers of doses recommended, whereas evolution of Omicron sublineages raises questions about ongoing vaccine effectiveness. Methods: We estimated effectiveness of monovalent COVID-19 mRNA booster vaccination versus two-dose primary series during a period of Omicron variant virus circulation in a community cohort with active illness surveillance. Hazard ratios comparing SARS-CoV-2 infection between booster versus primary series vaccinated individuals were estimated using Cox proportional hazards models with time-varying booster status. Models were adjusted for age and prior SARS-CoV-2 infection. The effectiveness of a second booster among adults ≥50 years of age was similarly estimated. Results: The analysis included 883 participants ranging in age, from 5 to >90 years. Relative effectiveness was 51% (95% CI: 34%, 64%) favoring the booster compared with primary series vaccination and did not vary by prior infection status. Relative effectiveness was 74% (95% CI: 57%, 84%) at 15 to 90 days after booster receipt, but declined to 42% (95% CI: 16%, 61%) after 91 to 180 days, and to 36% (95% CI: 3%, 58%) after 180 days. The relative effectiveness of a second booster compared to a single booster was 24% (95% CI: -40% to 61%). Conclusions: An mRNA vaccine booster dose added significant protection against SARS-CoV-2 infection, but protection decreased over time. A second booster did not add significant protection for adults ≥50 years of age. Uptake of recommended bivalent boosters should be encouraged to increase protection against Omicron BA.4/BA.5 sublineages.

Influenza Vaccine Effectiveness Among Children: 2011-2020.

BACKGROUND AND OBJECTIVES: Infants and children are at increased risk of severe influenza virus infection and its complications. Influenza vaccine effectiveness (VE) varies by age, influenza season, and influenza virus type/subtype. This study's objective was to examine the effectiveness of inactivated influenza vaccine against outpatient influenza illness in the pediatric population over 9 influenza seasons after the 2009 A(H1N1) pandemic. METHODS: During the 2011-2012 through the 2019-2020 influenza seasons at outpatient clinics at 5 sites of the US Influenza Vaccine Effectiveness Network, children aged 6 months to 17 years with an acute respiratory illness were tested for influenza using real-time, reverse-transcriptase polymerase chain reaction. Vaccine effectiveness was estimated using a test-negative design. RESULTS: Among 24 148 enrolled children, 28% overall tested positive for influenza, 3017 tested positive for influenza A(H3N2), 1459 for influenza A(H1N1)pdm09, and 2178 for influenza B. Among all enrollees, 39% overall were vaccinated, with 29% of influenza cases and 43% of influenza-negative controls vaccinated. Across all influenza seasons, the pooled VE for any influenza was 46% (95% confidence interval, 43-50). Overall and by type/subtype, VE against influenza illness was highest among children in the 6- to 59-month age group compared with older pediatric age groups. VE was lowest for influenza A(H3N2) virus infection. CONCLUSIONS: Analysis of multiple seasons suggested substantial benefit against outpatient illness. Investigation of host-specific or virus-related mechanisms that may result in differences by age and virus type/subtype may help further efforts to promote increased vaccination coverage and other influenza-related preventative measures.

Interim Estimates of 2022-23 Seasonal Influenza Vaccine Effectiveness - Wisconsin, October 2022-February 2023.

In the United States, 2022-23 influenza activity began earlier than usual, increasing in October 2022, and has been associated with high rates of hospitalizations among children* (1). Influenza A(H3N2) represented most influenza viruses detected and subtyped during this period, but A(H1N1)pdm09 viruses cocirculated as well. Most viruses characterized were in the same genetic subclade as and antigenically similar to the viruses included in the 2022-23 Northern Hemisphere influenza vaccine (1,2). Effectiveness of influenza vaccine varies by season, influenza virus subtype, and antigenic match with circulating viruses. This interim report used data from two concurrent studies conducted at Marshfield Clinic Health System (MCHS) in Wisconsin during October 23, 2022-February 10, 2023, to estimate influenza vaccine effectiveness (VE). Overall, VE was 54% against medically attended outpatient acute respiratory illness (ARI) associated with laboratory-confirmed influenza A among patients aged 6 months-64 years. In a community cohort of children and adolescents aged <18 years, VE was 71% against symptomatic laboratory-confirmed influenza A virus infection. These interim analyses indicate that influenza vaccination substantially reduced the risk for medically attended influenza among persons aged <65 years and for symptomatic influenza in children and adolescents. Annual influenza vaccination is the best strategy for preventing influenza and its complications. CDC recommends that health care providers continue to administer annual influenza vaccine to persons aged ≥6 months as long as influenza viruses are circulating (2).

Safety of measles, mumps, and rubella vaccine in adolescents and adults in the vaccine safety Datalink.

Background: Measles, mumps, and rubella vaccine (MMR) is routinely administered to children; however, adolescents and adults may receive MMR for various reasons. Safety studies in adolescents and adults are limited. We report on safety of MMR in this age group in the Vaccine Safety Datalink. Methods: We included adolescents (aged 9-17 years) and adults (aged ≥ 18 years) who received ≥ 1 dose of MMR from January 1, 2010-December 31, 2018. Pre-specified outcomes were identified by diagnosis codes. Clinically serious outcomes included anaphylaxis, encephalitis/myelitis, Guillain-Barré syndrome, immune thrombocytopenia, meningitis, and seizure. Non-serious outcomes were allergic reaction, arthropathy, fever, injection site reaction, lymphadenopathy, non-specific reaction, parotitis, rash, and syncope. All serious outcomes underwent medical record review. Outcome-specific incidence was calculated in pre-defined post-vaccination windows. A self-controlled risk interval design was used to determine the relative risk of each outcome in a risk window after vaccination compared to a more distal control window. Results: During the study period, 276,327 MMR doses were administered to adolescents and adults. Mean age of vaccinees was 34.8 years; 65.8 % were female; 53.2 % of doses were administered simultaneously with ≥ 1 other vaccine. Serious outcomes were rare, with incidence ≤ 6 per 100,000 doses for each outcome assessed, and none had a significant elevation in incidence during the risk window compared to the control window. Incidence of non-serious outcomes per 100,000 doses ranged from 3.4 for parotitis to 263.0 for arthropathy. Other common outcomes included injection site reaction and rash (157.0 and 112.9 per 100,000 doses, respectively). Significantly more outcomes were observed during the risk window compared to the control window for all non-serious outcomes except parotitis. Some variability was observed by sex and age group. Conclusion: Serious outcomes after MMR are rare in adolescents and adults, but vaccinees should be counseled regarding anticipated local and systemic non-serious adverse events.

Household Transmission of Influenza A Viruses in 2021-2022.

Importance: Influenza virus infections declined globally during the COVID-19 pandemic. Loss of natural immunity from lower rates of influenza infection and documented antigenic changes in circulating viruses may have resulted in increased susceptibility to influenza virus infection during the 2021-2022 influenza season. Objective: To compare the risk of influenza virus infection among household contacts of patients with influenza during the 2021-2022 influenza season with risk of influenza virus infection among household contacts during influenza seasons before the COVID-19 pandemic in the US. Design, Setting, and Participants: This prospective study of influenza transmission enrolled households in 2 states before the COVID-19 pandemic (2017-2020) and in 4 US states during the 2021-2022 influenza season. Primary cases were individuals with the earliest laboratory-confirmed influenza A(H3N2) virus infection in a household. Household contacts were people living with the primary cases who self-collected nasal swabs daily for influenza molecular testing and completed symptom diaries daily for 5 to 10 days after enrollment. Exposures: Household contacts living with a primary case. Main Outcomes and Measures: Relative risk of laboratory-confirmed influenza A(H3N2) virus infection in household contacts during the 2021-2022 season compared with prepandemic seasons. Risk estimates were adjusted for age, vaccination status, frequency of interaction with the primary case, and household density. Subgroup analyses by age, vaccination status, and frequency of interaction with the primary case were also conducted. Results: During the prepandemic seasons, 152 primary cases (median age, 13 years; 3.9% Black; 52.0% female) and 353 household contacts (median age, 33 years; 2.8% Black; 54.1% female) were included and during the 2021-2022 influenza season, 84 primary cases (median age, 10 years; 13.1% Black; 52.4% female) and 186 household contacts (median age, 28.5 years; 14.0% Black; 63.4% female) were included in the analysis. During the prepandemic influenza seasons, 20.1% (71/353) of household contacts were infected with influenza A(H3N2) viruses compared with 50.0% (93/186) of household contacts in 2021-2022. The adjusted relative risk of A(H3N2) virus infection in 2021-2022 was 2.31 (95% CI, 1.86-2.86) compared with prepandemic seasons. Conclusions and Relevance: Among cohorts in 5 US states, there was a significantly increased risk of household transmission of influenza A(H3N2) in 2021-2022 compared with prepandemic seasons. Additional research is needed to understand reasons for this association.

Prior SARS-CoV-2 Infection and COVID-19 Vaccine Effectiveness against Outpatient Illness during Widespread Circulation of SARS-CoV-2 Omicron Variant, US Flu VE Network.

Background: We estimated combined protection conferred by prior SARS-CoV-2 infection and COVID-19 vaccination against COVID-19-associated acute respiratory illness (ARI). Methods: During SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variant circulation between October 2021 and April 2022, prospectively enrolled adult patients with outpatient ARI had respiratory and filter paper blood specimens collected for SARS-CoV-2 molecular testing and serology. Dried blood spots were tested for immunoglobulin-G antibodies against SARS-CoV-2 nucleocapsid (NP) and spike protein receptor binding domain antigen using a validated multiplex bead assay. Evidence of prior SARS-CoV-2 infection also included documented or self-reported laboratory-confirmed COVID-19. We used documented COVID-19 vaccination status to estimate vaccine effectiveness (VE) by multivariable logistic regression by prior infection status. Results: 455 (29%) of 1577 participants tested positive for SARS-CoV-2 infection at enrollment; 209 (46%) case-patients and 637 (57%) test-negative patients were NP seropositive, had documented previous laboratory-confirmed COVID-19, or self-reported prior infection. Among previously uninfected patients, three-dose VE was 97% (95% confidence interval [CI], 60%- 99%) against Delta, but not statistically significant against Omicron. Among previously infected patients, three-dose VE was 57% (CI, 20%-76%) against Omicron; VE against Delta could not be estimated. Conclusions: Three mRNA COVID-19 vaccine doses provided additional protection against SARS-CoV-2 Omicron variant-associated illness among previously infected participants.

Active Postlicensure Safety Surveillance for Recombinant Zoster Vaccine Using Electronic Health Record Data.

Recombinant zoster vaccine (RZV) (Shingrix; GlaxoSmithKline, Brentford, United Kingdom) is an adjuvanted glycoprotein vaccine that was licensed in 2017 to prevent herpes zoster (shingles) and its complications in older adults. In this prospective, postlicensure Vaccine Safety Datalink study using electronic health records, we sequentially monitored a real-world population of adults aged ≥50 years who received care in multiple US Vaccine Safety Datalink health systems to identify potentially increased risks of 10 prespecified health outcomes, including stroke, anaphylaxis, and Guillain-Barré syndrome (GBS). Among 647,833 RZV doses administered from January 2018 through December 2019, we did not detect a sustained increased risk of any monitored outcome for RZV recipients relative to either historical (2013-2017) recipients of zoster vaccine live, a live attenuated virus vaccine (Zostavax; Merck & Co., Inc., Kenilworth, New Jersey), or contemporary non-RZV vaccine recipients who had an annual well-person visit during the 2018-2019 study period. We confirmed prelicensure trial findings of increased risks of systemic and local reactions following RZV. Our study provides additional reassurance about the overall safety of RZV. Despite a large sample, uncertainty remains regarding potential associations with GBS due to the limited number of confirmed GBS cases that were observed.

Influenza Vaccine Effectiveness Against Influenza A(H3N2)-Related Illness in the United States During the 2021-2022 Influenza Season.

BACKGROUND: In the United States, influenza activity during the 2021-2022 season was modest and sufficient enough to estimate influenza vaccine effectiveness (VE) for the first time since the beginning of the coronavirus disease 2019 pandemic. We estimated influenza VE against laboratory-confirmed outpatient acute illness caused by predominant A(H3N2) viruses. METHODS: Between October 2021 and April 2022, research staff across 7 sites enrolled patients aged ≥6 months seeking outpatient care for acute respiratory illness with cough. Using a test-negative design, we assessed VE against influenza A(H3N2). Due to strong correlation between influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination, participants who tested positive for SARS-CoV-2 were excluded from VE estimations. Estimates were adjusted for site, age, month of illness, race/ethnicity, and general health status. RESULTS: Among 6260 participants, 468 (7%) tested positive for influenza only, including 440 (94%) for A(H3N2). All 206 sequenced A(H3N2) viruses were characterized as belonging to genetic group 3C.2a1b subclade 2a.2, which has antigenic differences from the 2021-2022 season A(H3N2) vaccine component that belongs to clade 3C.2a1b subclade 2a.1. After excluding 1948 SARS-CoV-2-positive patients, 4312 patients were included in analyses of influenza VE; 2463 (57%) were vaccinated against influenza. Effectiveness against A(H3N2) for all ages was 36% (95% confidence interval, 20%-49%) overall. CONCLUSIONS: Influenza vaccination in 2021-2022 provided protection against influenza A(H3N2)-related outpatient visits among young persons.

Extended surveillance to assess safety of 9-valent human papillomavirus vaccine.

The safety of 9-valent HPV vaccine (9vHPV) has been established with regard to common and uncommon adverse events. However, investigation of rare and severe adverse events requires extended study periods to capture rare outcomes. This observational cohort study investigated the occurrence of three rare and serious adverse events following 9-valent human papillomavirus (9vHPV) vaccination compared to other vaccinations, in US individuals 9-26 years old, using electronic health record data from the Vaccine Safety Datalink (VSD). We searched for occurrences of Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), and stroke following 9vHPV vaccination from October 4, 2015, through January 2, 2021. We compared the risks of GBS, CIDP, and stroke following 9vHPV vaccination to risks of those outcomes following comparator vaccines commonly given to this age group (Td, Tdap, MenACWY, hepatitis A, and varicella vaccines) from January 1, 2007, through January 2, 2021. We observed 1.2 cases of stroke, 0.3 cases of GBS, and 0.1 cases of CIDP per 100,000 doses of 9vHPV vaccine. After observing more than 1.8 million doses of 9vHPV, we identified no statistically significant increase in risks associated with 9vHPV vaccination for any of these adverse events, either combined or stratified by age (9-17 years of age vs. 18-26 years of age) and sex (males vs. females). Our findings provide additional evidence supporting 9vHPV vaccine safety, over longer time frames and for more serious and rare adverse events.

Burden of medically attended influenza infection and cases averted by vaccination - United States, 2016/17 through 2018/19 influenza seasons.

BACKGROUND: Epidemics of seasonal influenza vary in intensity annually, and influenza vaccine effectiveness (VE) fluctuates based in part on antigenic match to circulating viruses. We estimated the incidence of influenza and influenza cases averted by vaccination in four ambulatory care sites in the United States, during seasons when overall influenza VE ranged from 29% to 40%. METHODS: We conducted active surveillance for influenza at ambulatory care settings at four sites within the United States Influenza Vaccine Effectiveness Network. We extrapolated the total number of influenza cases in the source populations served by these organizations based on incidence of medically attended acute respiratory illness in the source population and influenza test results in those actively tested for influenza. We estimated the number of medically attended influenza cases averted based on incidence, vaccine coverage, and VE. RESULTS: From 2016/17 through 2018/19, incidence of ambulatory visits for laboratory-confirmed influenza ranged from 31 to 51 per 1,000 population. Incidence was highest in children aged 9-17 years (range, 56 to 81 per 1,000) and lowest in adults aged 18-49 years (range, 23-32 per 1,000). Medically attended cases averted by vaccination ranged from a high of 46.6 (95 % CI, 12.1- 91.9) per 1,000 vaccinees in children aged 6 months to 8 years, to a low of 6.9 (95 % CI, -5.1- 27.3) per 1,000 vaccinees in adults aged ≥ 65 years. DISCUSSION: Even in seasons with low vaccine effectiveness for a particular virus subtype, influenza vaccines can still lead to clinically meaningful reductions in ambulatory care visits for influenza.