Interim Influenza Vaccine Effectiveness Against Laboratory-Confirmed Influenza - California, October 2023-January 2024.

Surveillance data can provide rapid, within-season influenza vaccine effectiveness (VE) estimates to guide public health recommendations. Mandatory reporting of influenza vaccine administration to California's immunization information registry began January 1, 2023, and mandatory reporting of all influenza laboratory test results, including negative results, was instituted in California on June 15, 2023. These data, collected by the California Department of Public Health during October 1, 2023-January 31, 2024, were used to calculate interim influenza VE against laboratory-confirmed influenza by comparing the odds of vaccination among case-patients (persons who received a positive influenza laboratory test result) and control patients (those who received a negative influenza laboratory test result). VE was calculated as 1 - adjusted odds ratio using mixed-effects logistic regression, with age, race, and ethnicity as fixed effects and specimen collection week and county as random effects. Overall, during October 1, 2023-January 31, 2024, estimated VE was 45% among persons aged ≥6 months, 56% among children and adolescents aged 6 months-17 years, 48% among adults aged 18-49 years, 36% among those aged 50-64 years, and 30% among those aged ≥65 years. Consistent with some previous influenza seasons, influenza vaccination provided moderate protection against laboratory-confirmed influenza among infants, children, adolescents, and adults. All persons aged ≥6 months without a contraindication to vaccination should receive annual influenza vaccination to reduce influenza illness, severe influenza, and strain on health care resources. Influenza vaccination remains the best way to prevent influenza.

Receipt of COVID-19 and seasonal influenza vaccines in California (USA) during the 2021-2022 influenza season.

BACKGROUND: Despite lower circulation of influenza virus throughout 2020-2022 during the COVID-19 pandemic, seasonal influenza vaccination has remained a primary tool to reduce influenza-associated illness and death. The relationship between the decision to receive a COVID-19 vaccine and/or an influenza vaccine is not well understood. METHODS: We assessed predictors of receipt of 2021-2022 influenza vaccine in a secondary analysis of data from a case-control study enrolling individuals who received SARS-CoV-2 testing. We used mixed effects logistic regression to estimate factors associated with receipt of seasonal influenza vaccine. We also constructed multinomial adjusted marginal probability models of being vaccinated for COVID-19 only, seasonal influenza only, or both as compared with receipt of neither vaccination. RESULTS: Among 1261 eligible participants recruited between 22 October 2021-22 June 2022, 43% (545) were vaccinated with both seasonal influenza vaccine and >1 dose of a COVID-19 vaccine, 34% (426) received >1 dose of a COVID-19 vaccine only, 4% (49) received seasonal influenza vaccine only, and 19% (241) received neither vaccine. Receipt of >1 COVID-19 vaccine dose was associated with seasonal influenza vaccination (adjusted odds ratio [aOR]: 3.72; 95% confidence interval [CI]: 2.15-6.43); this association was stronger among participants receiving >1 COVID-19 booster dose (aOR = 16.50 [10.10-26.97]). Compared with participants testing negative for SARS- CoV-2 infection, participants testing positive had lower odds of receipt of 2021-2022 seasonal influenza vaccine (aOR = 0.64 [0.50-0.82]). CONCLUSIONS: Recipients of a COVID-19 vaccine were more likely to receive seasonal influenza vaccine during the 2021-2022 season. Factors associated with individuals' likelihood of receiving COVID-19 and seasonal influenza vaccines will be important to account for in future studies of vaccine effectiveness against both conditions. Participants who tested positive for SARS-CoV-2 in our sample were less likely to have received seasonal influenza vaccine, suggesting an opportunity to offer influenza vaccination before or after a COVID-19 diagnosis.

Evaluation of FluSight influenza forecasting in the 2021-22 and 2022-23 seasons with a new target laboratory-confirmed influenza hospitalizations.

Accurate forecasts can enable more effective public health responses during seasonal influenza epidemics. Forecasting teams were asked to provide national and jurisdiction-specific probabilistic predictions of weekly confirmed influenza hospital admissions for one through four weeks ahead for the 2021-22 and 2022-23 influenza seasons. Across both seasons, 26 teams submitted forecasts, with the submitting teams varying between seasons. Forecast skill was evaluated using the Weighted Interval Score (WIS), relative WIS, and coverage. Six out of 23 models outperformed the baseline model across forecast weeks and locations in 2021-22 and 12 out of 18 models in 2022-23. Averaging across all forecast targets, the FluSight ensemble was the 2nd most accurate model measured by WIS in 2021-22 and the 5th most accurate in the 2022-23 season. Forecast skill and 95% coverage for the FluSight ensemble and most component models degraded over longer forecast horizons and during periods of rapid change. Current influenza forecasting efforts help inform situational awareness, but research is needed to address limitations, including decreased performance during periods of changing epidemic dynamics.

Disparities in COVID-19 fatalities among working Californians.

BACKGROUND: Information on U.S. COVID-19 mortality rates by occupation is limited. We aimed to characterize 2020 COVID-19 fatalities among working Californians to inform preventive strategies. METHODS: We identified laboratory-confirmed COVID-19 fatalities with dates of death in 2020 by matching death certificates to the state's COVID-19 case registry. Working status for decedents aged 18-64 years was determined from state employment records, death certificates, and case registry data and classified as "confirmed working," "likely working," or "not working." We calculated age-adjusted overall and occupation-specific COVID-19 mortality rates using 2019 American Community Survey denominators. RESULTS: COVID-19 accounted for 8,050 (9.9%) of 81,468 fatalities among Californians 18-64 years old. Of these decedents, 2,486 (30.9%) were matched to state employment records and classified as "confirmed working." The remainder were classified as "likely working" (n = 4,121 [51.2%]) or "not working" (n = 1,443 [17.9%]) using death certificate and case registry data. Confirmed and likely working COVID-19 decedents were predominantly male (76.3%), Latino (68.7%), and foreign-born (59.6%), with high school or less education (67.9%); 7.8% were Black. The overall age-adjusted COVID-19 mortality rate was 30.0 per 100,000 workers (95% confidence interval [CI], 29.3-30.8). Workers in nine occupational groups had age-adjusted mortality rates higher than this overall rate, including those in farming (78.0; 95% CI, 68.7-88.2); material moving (77.8; 95% CI, 70.2-85.9); construction (62.4; 95% CI, 57.7-67.4); production (60.2; 95% CI, 55.7-65.0); and transportation (57.2; 95% CI, 52.2-62.5) occupations. While occupational differences in mortality were evident across demographic groups, mortality rates were three-fold higher for male compared with female workers and three- to seven-fold higher for Latino and Black workers compared with Asian and White workers. CONCLUSION: Californians in manual labor and in-person service occupations experienced disproportionate COVID-19 mortality, with the highest rates observed among male, Latino, and Black workers; these occupational group should be prioritized for prevention.

Influenza and SARS-CoV-2 Co-infections in California, USA, September 2020-April 2021.

During September 1, 2020-April 30, 2021, the California Department of Public Health, Richmond, California, USA, received 255 positive influenza molecular test results that matched with severe acute respiratory syndrome coronavirus 2 molecular test results; 58 (23%) persons were co-infected. Influenza activity was minimal in California, and co-infections were sporadic.

Racial/Ethnic Disparities In COVID-19 Exposure Risk, Testing, And Cases At The Subcounty Level In California.

With a population of forty million and substantial geographic variation in sociodemographics and health services, California is an important setting in which to study disparities. Its population (37.5 percent White, 39.1 percent Latino, 5.3 percent Black, and 14.4 percent Asian) experienced 59,258 COVID-19 deaths through April 14, 2021-the most of any state. We analyzed California's racial/ethnic disparities in COVID-19 exposure risks, testing rates, test positivity, and case rates through October 2020, combining data from 15.4 million SARS-CoV-2 tests with subcounty exposure risk estimates from the American Community Survey. We defined "high-exposure-risk" households as those with one or more essential workers and fewer rooms than inhabitants. Latino people in California are 8.1 times more likely to live in high-exposure-risk households than White people (23.6 percent versus 2.9 percent), are overrepresented in cumulative cases (3,784 versus 1,112 per 100,000 people), and are underrepresented in cumulative testing (35,635 versus 48,930 per 100,000 people). These risks and outcomes were worse for Latino people than for members of other racial/ethnic minority groups. Subcounty disparity analyses can inform targeting of interventions and resources, including community-based testing and vaccine access measures. Tracking COVID-19 disparities and developing equity-focused public health programming that mitigates the effects of systemic racism can help improve health outcomes among California's populations of color.

Public Health Responses to COVID-19 Outbreaks on Cruise Ships - Worldwide, February-March 2020.

An estimated 30 million passengers are transported on 272 cruise ships worldwide each year* (1). Cruise ships bring diverse populations into proximity for many days, facilitating transmission of respiratory illness (2). SARS-CoV-2, the virus that causes coronavirus disease (COVID-19) was first identified in Wuhan, China, in December 2019 and has since spread worldwide to at least 187 countries and territories. Widespread COVID-19 transmission on cruise ships has been reported as well (3). Passengers on certain cruise ship voyages might be aged ≥65 years, which places them at greater risk for severe consequences of SARS-CoV-2 infection (4). During February-March 2020, COVID-19 outbreaks associated with three cruise ship voyages have caused more than 800 laboratory-confirmed cases among passengers and crew, including 10 deaths. Transmission occurred across multiple voyages of several ships. This report describes public health responses to COVID-19 outbreaks on these ships. COVID-19 on cruise ships poses a risk for rapid spread of disease, causing outbreaks in a vulnerable population, and aggressive efforts are required to contain spread. All persons should defer all cruise travel worldwide during the COVID-19 pandemic.

Characteristics Associated With Delivery of an Infant With Congenital Syphilis and Missed Opportunities for Prevention-California, 2012 to 2014.

BACKGROUND: Congenital syphilis (CS), the transmission of Treponema pallidum from mother to fetus during pregnancy, can cause adverse birth outcomes. In 2012 to 2014, the CS rate in California increased more than 200% from 6.6 to 20.3 cases per 100,000 live births. Our objectives were to identify characteristics associated with delivering an infant with CS and missed opportunities for prevention among syphilis-infected pregnant women in California. METHODS: We linked California Department of Public Health syphilis surveillance records from women aged 15 to 45 years-diagnosed from March 13, 2012, to December 31, 2014-to birth records. We compared characteristics among mothers who delivered an infant with CS (CS mothers) with mothers who delivered an infant without CS (non-CS mothers) by using χ or Fisher exact tests. To visualize gaps in prevention among syphilis-infected pregnant women, we constructed a CS prevention cascade, a figure that shows steps to prevent CS. RESULTS: During the selected period, 2498 women were diagnosed as having syphilis, and 427 (17%) linked to birth records; 164 (38%) were defined as CS mothers and 263 (62%) as non-CS mothers. Mothers with CS were more likely than non-CS mothers to have their first prenatal care visit in the third trimester. High proportions of mothers in both groups reported high-risk sexual behaviors, methamphetamine use, or incarceration (13%-29%). The CS prevention cascade showed decrements of 5% to 11% in prenatal care receipt, testing, and treatment steps; only 62% of potential CS births were prevented. CONCLUSIONS: Multifaceted efforts are needed to address gaps in the CS prevention cascade and reduce CS cases in California.

Risk Factors Associated With Infant Deaths From Pertussis: A Case-Control Study.

BACKGROUND: In the current era, most pertussis deaths occur in infants <3 months of age. Leukocytosis with lymphocytosis and pneumonia are commonly observed among cases of severe pertussis. METHODS: Risk factors associated with fatal pertussis were identified by comparing fatal pertussis cases among patients <120 days of age occurring from 1 January 1998 through 26 December 2014, matched by age (<120 days), county of residence, and closest symptom onset date with 1-4 nonfatal hospitalized cases. California Department of Public Health surveillance data were reviewed to identify cases; demographics, clinical presentation, and course were abstracted from corresponding birth and medical records. Logistic regression and classification tree analyses were used to examine the risk of fatal pertussis with respect to identified factors. RESULTS: Fifty-three fatal infant pertussis cases were identified and compared with 183 nonfatal hospitalized pertussis cases. Fatal cases had significantly lower birth weight, younger gestational age, younger age at time of cough onset, and higher peak white blood cell (WBC) and lymphocyte counts. Fatal cases were less likely to have received macrolide antibiotics and more likely to have received steroids or nitric oxide and to develop pulmonary hypertension, seizures, encephalitis, and pneumonia. Additionally, exchange transfusion, extracorporeal membrane oxygenation, and intubation occurred significantly more frequently among fatal cases. In multivariate analyses, peak WBC count, birth weight, intubation, and receipt of nitric oxide were predictors of death. CONCLUSIONS: Early recognition of pertussis in young infants and treatment with appropriate antibiotic therapy are important in preventing death. Several risk factors are strongly associated with fatal pertussis in infants.

Pregnancy and severe influenza infection in the 2013-2014 influenza season.

OBJECTIVE: To describe the epidemiologic and clinical characteristics of critically ill pregnant and postpartum women with influenza infection reported in the 2013-2014 season. METHODS: The California Department of Public Health conducts surveillance for patients with laboratory-confirmed influenza who die or require hospitalization in intensive care units. For this case series, we reviewed data on pregnant and postpartum (6 weeks or less from delivery) women reported in the 2013-2014 influenza season. RESULTS: From September 29, 2013, through May 17, 2014, 17 pregnant women with severe influenza were reported. The median age was 29 years (range 17-44 years). Sixteen (94%) were in the second or third trimester. Fifteen (88%) patients were hospitalized, nine (53%) required mechanical ventilation, five (29%) required emergent cesarean delivery, and four (24%) died. Of 14 patients with available information, only two (14%) received influenza vaccination during pregnancy. Seven patients who tested positive by polymerase chain reaction also had rapid influenza diagnostic testing performed; only one (14%) had a positive rapid influenza diagnostic test results. Fifteen patients received antiviral treatment; four (27%) began treatment within 48 hours of symptom onset. One additional patient was 36 days postpartum and required intensive care unit admission and mechanical ventilation for influenza-associated acute respiratory distress syndrome. CONCLUSION: Influenza remains a significant cause of morbidity and mortality in pregnant and postpartum women; in our series, a majority were not vaccinated. During the influenza season, pregnant women with suspected influenza should receive prompt empiric antiviral therapy, regardless of rapid influenza diagnostic test results or vaccination status. LEVEL OF EVIDENCE: III.

Notes from the field: measles - California, January 1-April 18, 2014.

Measles is a highly contagious, acute viral illness that can lead to severe complications and death. Even patients who experience uncomplicated acute measles have a small risk for developing a devastating neurologic illness, subacute sclerosing panencephalitis, years after their infection. Measles was documented as eliminated (defined as interruption of continuous transmission lasting ≥12 months) in the United States in 2000; however, importation of measles cases and limited local transmission continue to occur. During January 1-April 18, 2014, the California Department of Public Health received reports of 58 confirmed measles cases, the highest number reported for that period since 1995. Patients ranged in age from 5 months to 60 years. Three (5%) patients were aged <12 months, six (10%) were aged 1-4 years, 17 (29%) were aged 5-19 years, and 32 (55%) were aged ≥20 years. As of April 18, there had been 12 hospitalizations, and no deaths had been reported. During 2000-2013, the median annual number of measles cases reported in California was nine (range = four to 40).

Neisseria gonorrhoeae outbreak: unintended consequences of electronic medical records and using an out-of-state laboratory-California, July 2009-February 2010.

Twenty of 37 gonorrhea cases identified during an outbreak were diagnosed at one health care organization that used an out-of-state laboratory. The results were transmitted into electronic medical records without provider notification. Delays in treatment and reporting were identified. Systems should be implemented to ensure provider notification of electronic laboratory results.

Exchange blood transfusion in the management of severe pertussis in young infants.

We analyzed data from 10 young infants who received exchange blood transfusions for management of severe pertussis. Our data are insufficient to address efficacy of the procedure, but our data, as well as previous reports in the literature, indicate that if the procedure is to be successful, it should be done before organ failure has occurred and immediately if shock/hypotension occur.

Characteristics of Severe Bordetella pertussis Infection Among Infants ≤90 Days of Age Admitted to Pediatric Intensive Care Units - Southern California, September 2009-June 2011.

BACKGROUND: Bordetella pertussis infection can cause severe illness and death among young infants. METHODS: We collected demographic and clinical information from the medical records of infants who were ≤90 days of age and hospitalized for pertussis in 5 Southern California pediatric intensive care units (PICUs) from September 1, 2009 to June 30, 2011. Infants who died or were diagnosed with pulmonary hypertension were considered to have more severe pertussis. RESULTS: Thirty-one infants were admitted to a participating PICU. Eight infants had more severe infections, 6 infants had pulmonary hypertension, and 4 infants died. The 8 infants with more severe infections had white blood cell counts that exceeded 30 000, heart rates that exceeded 170, and respiratory rates that exceeded 70 more rapidly after cough onset than the 23 infants with less severe illness. CONCLUSIONS: Identifying higher-risk infants earlier might allow for more rapid implementation of interventions.

Internet-based morbidity and mortality surveillance among Hurricane Katrina evacuees in Georgia.

INTRODUCTION: The Internet has revolutionized the way public health surveillance is conducted. Georgia has used it for notifiable disease reporting, electronic outbreak management, and early event detection. We used it in our public health response to the 125,000 Hurricane Katrina evacuees who came to Georgia. METHODS: We developed Internet-based surveillance forms for evacuation shelters and an Internet-based death registry. District epidemiologists, hospital-based physicians, and medical examiners/coroners electronically completed the forms. We analyzed these data and data from emergency departments used by the evacuees. RESULTS: Shelter residents and patients who visited emergency departments reported primarily chronic diseases. Among 33 evacuee deaths, only 2 were from infectious diseases, and 1 was indirectly related to the hurricane. CONCLUSION: The Internet was essential to collect health data from multiple locations, by many different people, and for multiple types of health encounters during Georgia's Hurricane Katrina public health response.

Influenza-associated deaths among children in the United States, 2003-2004.

BACKGROUND: Although influenza is common among children, pediatric mortality related to laboratory-confirmed influenza has not been assessed nationally. METHODS: During the 2003-2004 influenza season, we requested that state health departments report any death associated with laboratory-confirmed influenza in a U.S. resident younger than 18 years of age. Case reports, medical records, and autopsy reports were reviewed, and available influenza-virus isolates were analyzed at the Centers for Disease Control and Prevention. RESULTS: One hundred fifty-three influenza-associated deaths among children were reported by 40 state health departments. The median age of the children was three years, and 96 of them (63 percent) were younger than five years old. Forty-seven of the children (31 percent) died outside a hospital setting, and 45 (29 percent) died within three days after the onset of illness. Bacterial coinfections were identified in 24 of the 102 children tested (24 percent). Thirty-three percent of the children had an underlying condition recognized to increase the risk of influenza-related complications, and 20 percent had other chronic conditions; 47 percent had previously been healthy. Chronic neurologic or neuromuscular conditions were present in one third. The mortality rate was highest among children younger than six months of age (0.88 per 100,000 children; 95 percent confidence interval, 0.52 to 1.39 per 100,000). CONCLUSIONS: A substantial number of influenza-associated deaths occurred among U.S. children during the 2003-2004 influenza season. High priority should be given to improvements in influenza-vaccine coverage and improvements in the diagnosis and treatment of influenza to reduce childhood mortality from influenza.

Surveillance for influenza--United States, 1997-98, 1998-99, and 1999-00 seasons.

PROBLEM/CONDITION: In the United States, influenza epidemics occur nearly every winter and are responsible for substantial morbidity and mortality, including an average of approximately 114,000 hospitalizations and 20,000 deaths/year. REPORTING PERIOD: This report summarizes both actively and passively collected U.S. influenza surveillance data from October 1997 through September 2000. DESCRIPTION OF SYSTEM: During each October-May in the period covered, CDC received weekly reports from 1) approximately 120 World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories in the United States regarding influenza virus isolations; 2) approximately 230, 375, and 430 sentinel physicians during 1997-98, 1998-99, and 1999-00, respectively, regarding their total number of patient visits and the number of visits for influenza-like illness (ILI); and 3) state and territorial epidemiologists regarding estimates of local influenza activity. WHO collaborating laboratories also submitted influenza isolates to CDC for antigenic analysis. Throughout the year, the vital statistics offices in 122 cities reported weekly on deaths related to pneumonia and influenza (P&I). RESULTS: During the 1997-98 influenza season, influenza A(H3N2) was the most frequently isolated influenza virus type/subtype. Influenza A(H1N1) and B viruses were reported infrequently. The proportion of respiratory specimens testing positive for influenza peaked at 28% in late January. The longest period of sustained excess mortality (when the percentage of deaths attributed to P&I exceeded the epidemic threshold) was 10 consecutive weeks. P&I mortality peaked at 9.8% in January. Visits for ILI to sentinel physicians exceeded baseline levels for 7 weeks and peaked at 5% in mid-January through early February. A total of 45 state epidemiologists reported regional or widespread activity at the peak of the season. During the 1998-99 season, influenza A(H3N2) viruses predominated; however, influenza B viruses were also identified throughout the United States. Influenza A(H1N1) viruses were identified rarely. The proportion of respiratory specimens testing positive for influenza peaked at 28% in early February. P&I mortality exceeded the epidemic threshold for 12 consecutive weeks and peaked at 9.7% in early March. Visits for ILI to sentinel physicians exceeded baseline levels for 7 weeks and peaked at 5% in early through mid-February. Forty-three state epidemiologists reported regional or widespread activity at the peak of the season. During the 1999-00 season, influenza A(H3N2) viruses predominated, but influenza A(H1N1) and B viruses also were identified. The proportion of respiratory specimens testing positive for influenza peaked at 31% in mid- to late December. The proportion of deaths attributed to P&I exceeded the epidemic threshold for 13 consecutive weeks and peaked at 11.2% in mid-January. Visits to sentinel physicians for ILI exceeded baseline levels 4 consecutive weeks and peaked at 6% in late December. Forty-four state epidemiologists reported regional or widespread activity at the peak of the season. INTERPRETATION: Influenza A(H1N1), A(H3N2), and B viruses circulated during 1997-2000, but influenza A(H3N2) was the most frequently reported virus type/subtype during all three seasons. Influenza A(H3N2) is the virus type/subtype most frequently associated with excess P&I mortality. Influenza activity during all three seasons occurred at moderate to severe levels, and excess P&I mortality was reported during > or = 10 weeks each year. PUBLIC HEALTH ACTIONS: CDC conducts active national surveillance during each October-May to detect the emergence and spread of influenza virus variants and to monitor influenza-related morbidity and mortality. Surveillance data are provided weekly throughout the influenza season to public health officials, WHO, and health-care providers and are used to guide vaccine strain selection, prevention and control activities, and patient care. Influenza vaccination is the most effective means for reducing the yearly effect of influenza. Typically, one or two of the influenza vaccine component viruses are updated each year so that vaccine strains will closely match circulating viruses. Surveillance data will continue to be used to select vaccine strains and to monitor the match between vaccine strains and the currently circulating viruses.