Frequency of Children Diagnosed with Perinatal Hepatitis C, United States, 2018-2020.

We describe hepatitis C testing of 47 (2%) of 2,266 children diagnosed with perinatal hepatitis C who were exposed during 2018-2020 in 7 jurisdictions in the United States. Expected frequency of perinatal transmission is 5.8%, indicating only one third of the cases in this cohort were reported to public health authorities.

Preliminary Findings of mRNA Covid-19 Vaccine Safety in Pregnant Persons.

BACKGROUND: Many pregnant persons in the United States are receiving messenger RNA (mRNA) coronavirus disease 2019 (Covid-19) vaccines, but data are limited on their safety in pregnancy. METHODS: From December 14, 2020, to February 28, 2021, we used data from the "v-safe after vaccination health checker" surveillance system, the v-safe pregnancy registry, and the Vaccine Adverse Event Reporting System (VAERS) to characterize the initial safety of mRNA Covid-19 vaccines in pregnant persons. RESULTS: A total of 35,691 v-safe participants 16 to 54 years of age identified as pregnant. Injection-site pain was reported more frequently among pregnant persons than among nonpregnant women, whereas headache, myalgia, chills, and fever were reported less frequently. Among 3958 participants enrolled in the v-safe pregnancy registry, 827 had a completed pregnancy, of which 115 (13.9%) resulted in a pregnancy loss and 712 (86.1%) resulted in a live birth (mostly among participants with vaccination in the third trimester). Adverse neonatal outcomes included preterm birth (in 9.4%) and small size for gestational age (in 3.2%); no neonatal deaths were reported. Although not directly comparable, calculated proportions of adverse pregnancy and neonatal outcomes in persons vaccinated against Covid-19 who had a completed pregnancy were similar to incidences reported in studies involving pregnant women that were conducted before the Covid-19 pandemic. Among 221 pregnancy-related adverse events reported to the VAERS, the most frequently reported event was spontaneous abortion (46 cases). CONCLUSIONS: Preliminary findings did not show obvious safety signals among pregnant persons who received mRNA Covid-19 vaccines. However, more longitudinal follow-up, including follow-up of large numbers of women vaccinated earlier in pregnancy, is necessary to inform maternal, pregnancy, and infant outcomes.

CDC Recommendations for Hepatitis C Testing Among Perinatally Exposed Infants and Children - United States, 2023.

The elimination of hepatitis C is a national priority (https://www.hhs.gov/sites/default/files/Viral-Hepatitis-National-Strategic-Plan-2021-2025.pdf). During 2010-2021, hepatitis C virus (HCV) acute and chronic infections (hereinafter referred to as HCV infections) increased in the United States, consequences of which include cirrhosis, liver cancer, and death. Rates of acute infections more than tripled among reproductive-aged persons during this time (from 0.8 to 2.5 per 100,000 population among persons aged 20-29 years and from 0.6 to 3.5 among persons aged 30-39 years). Because acute HCV infection can lead to chronic infection, this has resulted in increasing rates of HCV infections during pregnancy. Approximately 6%-7% of perinatally exposed (i.e., exposed during pregnancy or delivery) infants and children will acquire HCV infection. Curative direct-acting antiviral therapy is approved by the Food and Drug Administration for persons aged ≥3 years. However, many perinatally infected children are not tested or linked to care. In 2020, because of continued increases in HCV infections in the United States, CDC released universal screening recommendations for adults, which included recommendations for screening for pregnant persons during each pregnancy (Schillie S, Wester C, Osborne M, Wesolowski L, Ryerson AB. CDC recommendations for hepatitis C screening among adults-United States, 2020. MMWR Recomm Rep 2020;69[No. RR-2]:1-17). This report introduces four new CDC recommendations: 1) HCV testing of all perinatally exposed infants with a nucleic acid test (NAT) for detection of HCV RNA at age 2-6 months; 2) consultation with a health care provider with expertise in pediatric hepatitis C management for all infants and children with detectable HCV RNA; 3) perinatally exposed infants and children with an undetectable HCV RNA result at or after age 2 months do not require further follow-up unless clinically warranted; and 4) a NAT for HCV RNA is recommended for perinatally exposed infants and children aged 7-17 months who previously have not been tested, and a hepatitis C virus antibody (anti-HCV) test followed by a reflex NAT for HCV RNA (when anti-HCV is reactive) is recommended for perinatally exposed children aged ≥18 months who previously have not been tested. Proper identification of perinatally infected children, referral to care, and curative treatment are critical to achieving the goal of hepatitis C elimination.

Screening and Testing for Hepatitis B Virus Infection: CDC Recommendations - United States, 2023.

Chronic hepatitis B virus (HBV) infection can lead to substantial morbidity and mortality. Although treatment is not considered curative, antiviral treatment, monitoring, and liver cancer surveillance can reduce morbidity and mortality. Effective vaccines to prevent hepatitis B are available. This report updates and expands CDC's previously published Recommendations for Identification and Public Health Management of Persons with Chronic Hepatitis B Virus Infection (MMWR Recomm Rep 2008;57[No. RR-8]) regarding screening for HBV infection in the United States. New recommendations include hepatitis B screening using three laboratory tests at least once during a lifetime for adults aged ≥18 years. The report also expands risk-based testing recommendations to include the following populations, activities, exposures, or conditions associated with increased risk for HBV infection: persons incarcerated or formerly incarcerated in a jail, prison, or other detention setting; persons with a history of sexually transmitted infections or multiple sex partners; and persons with a history of hepatitis C virus infection. In addition, to provide increased access to testing, anyone who requests HBV testing should receive it, regardless of disclosure of risk, because many persons might be reluctant to disclose stigmatizing risks.

Use of an Additional Updated 2023-2024 COVID-19 Vaccine Dose for Adults Aged ≥65 Years: Recommendations of the Advisory Committee on Immunization Practices - United States, 2024.

COVID-19 remains an important public health threat, despite overall decreases in COVID-19-related severe disease since the start of the COVID-19 pandemic. COVID-19-associated hospitalization rates remain higher among adults aged ≥65 years relative to rates in younger adults, adolescents, and children; during October 2023-January 2024, 67% of all COVID-19-associated hospitalizations were among persons aged ≥65 years. On September 12, 2023, CDC's Advisory Committee on Immunization Practices (ACIP) recommended updated (2023-2024 Formula) COVID-19 vaccination with a monovalent XBB.1.5-derived vaccine for all persons aged ≥6 months to protect against severe COVID-19-associated illness and death. Because SARS-CoV-2 continues to circulate throughout the year, and because of the increased risk for COVID-19-related severe illness in persons aged ≥65 years, the protection afforded by updated vaccines against JN.1 and other currently circulating variants, and the expected waning of vaccine-conferred protection against disease, on February 28, 2024, ACIP recommended all persons aged ≥65 years receive 1 additional dose of the updated (2023-2024 Formula) COVID-19 vaccine. Implementation of these recommendations is expected to enhance immunity that might have waned and decrease the risk for severe COVID-19-associated outcomes, including death, among persons aged ≥65 years.

Birth Outcomes Among People with Hepatitis C in Pregnancy - Three U.S. States, 2018-2021.

INTRODUCTION: There are limited and conflicting data regarding the impact of hepatitis C in pregnancy on adverse birth outcomes. METHODS: Using the Surveillance for Emerging Threats to Pregnant People and Infants Network (SET-NET), a large surveillance cohort, we describe birth outcomes among a cohort of people with HCV in pregnancy in total and by reported substance use. RESULTS: Among 1418 infants, 89% were born to people with reported substance use during pregnancy. The proportion born preterm was 20%, 13% were small-for-gestational age and 34% of term infants required intensive care. CONCLUSIONS: Assessments of recent changes to recommendations for HCV screening in pregnancy should evaluate the impact on maternal access to care for both HCV treatment as well as comorbidities such as substance use disorder which may contribute to adverse birth outcomes.

Cost-Effectiveness of Strategies to Identify Children with Perinatally Acquired Hepatitis C Infection.

OBJECTIVE: To determine the optimal testing strategy to identify children with perinatally acquired hepatitis C virus (HCV) infection. STUDY DESIGN: We used a decision-tree framework with a Markov disease progression model to conduct an economic analysis of 4 strategies, based on combinations of type and timing of test: anti-HCV with reflex to HCV RNA at 18 months among children known to be perinatally exposed (ie, baseline comparison strategy); HCV RNA testing at 2-6 months among infants known to be perinatally exposed (test strategy 1); universal anti-HCV with reflex to HCV RNA at 18 months among all children (test strategy 2); and universal HCV RNA testing at 2-6 months among all infants (test strategy 3). We estimated total cost, quality-adjusted life years, and disease sequalae for each strategy. RESULTS: Each of the 3 alternative testing strategies resulted in an increased number of children tested and improved health outcomes. HCV RNA testing at 2-6 months (test strategy 1) was cost-saving and resulted in a population-level difference in cost of $469 671. The 2 universal testing strategies resulted in an increase in quality-adjusted life years and an increase in total costs. CONCLUSIONS: Testing of perinatally exposed infants at age 2-6 months with a single HCV RNA test will reduce costs and improve health outcomes, preventing morbidity and mortality associated with complications from perinatal HCV infections.

Measles in the 21st Century: Progress Toward Achieving and Sustaining Elimination.

The global measles vaccination program has been extraordinarily successful in reducing measles-related disease and deaths worldwide. Eradication of measles is feasible because of several key attributes, including humans as the only reservoir for the virus, broad access to diagnostic tools that can rapidly detect measles-infectious persons, and availability of highly safe and effective measles-containing vaccines (MCVs). All 6 World Health Organization (WHO) regions have established measles elimination goals. Globally, during 2000-2018, measles incidence decreased by 66% (from 145 to 49 cases per million population) and deaths decreased by 73% (from 535 600 to 142 300), drastically reducing global disease burden. Routine immunization with MCV has been the cornerstone for the control and prevention of measles. Two doses of MCV are 97% effective in preventing measles, qualifying MCV as one of the most effective vaccines ever developed. Mild adverse events occur in <20% of recipients and serious adverse events are extremely rare. The economic benefits of measles vaccination are highlighted by an overall return on investment of 58 times the cost of the vaccine, supply chains, and vaccination. Because measles is one of the most contagious human diseases, maintenance of high (≥95%) 2-dose MCV coverage is crucial for controlling the spread of measles and successfully reaching measles elimination; however, the plateauing of global MCV coverage for nearly a decade and the global measles resurgence during 2018-2019 demonstrate that much work remains. Global commitments to increase community access to and demand for immunizations, strengthen national and regional partnerships for building public health infrastructure, and implement innovations that can overcome access barriers and enhance vaccine confidence, are essential to achieve a world free of measles.

Adverse Outcomes in Pregnant Women Hospitalized With Respiratory Syncytial Virus Infection: A Case Series.

We identified 10 women hospitalized with respiratory syncytial virus infection during pregnancy. Diagnoses included pneumonia/atelectasis (5), respiratory failure (2), and sepsis (2). Six had obstetrical complications during hospitalization, including 1 induced preterm birth. One required intensive care unit admission and mechanical ventilation. Four infants had complications at birth.

SARS-CoV-2 Infection Among Hospitalized Pregnant Women: Reasons for Admission and Pregnancy Characteristics - Eight U.S. Health Care Centers, March 1-May 30, 2020.

Pregnant women might be at increased risk for severe coronavirus disease 2019 (COVID-19), possibly related to changes in their immune system and respiratory physiology* (1). Further, adverse birth outcomes, such as preterm delivery and stillbirth, might be more common among pregnant women infected with SARS-CoV-2, the virus that causes COVID-19 (2,3). Information about SARS-CoV-2 infection during pregnancy is rapidly growing; however, data on reasons for hospital admission, pregnancy-specific characteristics, and birth outcomes among pregnant women hospitalized with SARS-CoV-2 infections are limited. During March 1-May 30, 2020, as part of Vaccine Safety Datalink (VSD)† surveillance of COVID-19 hospitalizations, 105 hospitalized pregnant women with SARS-CoV-2 infection were identified, including 62 (59%) hospitalized for obstetric reasons (i.e., labor and delivery or another pregnancy-related indication) and 43 (41%) hospitalized for COVID-19 illness without an obstetric reason. Overall, 50 (81%) of 62 pregnant women with SARS-CoV-2 infection who were admitted for obstetric reasons were asymptomatic. Among 43 pregnant women hospitalized for COVID-19, 13 (30%) required intensive care unit (ICU) admission, six (14%) required mechanical ventilation, and one died from COVID-19. Prepregnancy obesity was more common (44%) among pregnant women hospitalized for COVID-19 than that among asymptomatic pregnant women hospitalized for obstetric reasons (31%). Likewise, the rate of gestational diabetes (26%) among pregnant women hospitalized for COVID-19 was higher than it was among women hospitalized for obstetric reasons (8%). Preterm delivery occurred in 15% of pregnancies among 93 women who delivered, and stillbirths (fetal death at ≥20 weeks' gestation) occurred in 3%. Antenatal counseling emphasizing preventive measures (e.g., use of masks, frequent hand washing, and social distancing) might help prevent COVID-19 among pregnant women,§ especially those with prepregnancy obesity and gestational diabetes, which might reduce adverse pregnancy outcomes.

CDC's New Hepatitis C Virus Testing Recommendations for Perinatally Exposed Infants and Children: A Step Towards Hepatitis C Elimination.

New U.S. Centers for Disease Control and Prevention (CDC) guidelines for hepatitis C virus (HCV) testing of perinatally exposed infants and children released in 2023 recommend a nucleic acid test (NAT) for detection of HCV ribonucleic acid (i.e., NAT for HCV RNA) at 2-6 months of age to facilitate early identification and linkage to care for children with perinatally acquired HCV infection. Untreated hepatitis C can lead to cirrhosis, liver cancer, and premature death and is caused by HCV, a blood-borne virus transmitted most often among adults through injection drug use in the United States. Perinatal exposure from a birth parent with HCV infection is the most frequent mode of HCV transmission among infants and children. New HCV infections have been increasing since 2010, with the highest rates of infection among people aged 20-39 years, leading to an increasing prevalence of HCV infection during pregnancy. In 2020, the CDC recommended one-time HCV screening for all adults aged 18 years and older and for all pregnant persons during each pregnancy. Detecting HCV infection during pregnancy is key for the identification of pregnant persons, linkage to care for postpartum treatment, and identification of infants with perinatal exposure for HCV testing. It was previously recommended that children who were exposed to HCV during pregnancy receive an antibody to HCV (anti-HCV) test at 18 months of age; however, most children were lost to follow-up before testing occurred, leaving children with perinatal infection undiagnosed. The new strategy of testing perinatally exposed children at age 2-6 months was found to be cost-effective in increasing the identification of infants who might develop chronic hepatitis C. This report describes the current perinatal HCV testing recommendations and how they advance national hepatitis C elimination efforts by improving the health of pregnant and postpartum people and their children.

Progress and Unfinished Business: Hepatitis B in the United States, 1980-2019.

During 1990-2019, universal infant and childhood vaccination for hepatitis B resulted in a 99% decline in reported cases of acute hepatitis B among children, adolescents, and young adults aged <19 years in the United States; however, during 2010-2019, cases of acute hepatitis B plateaued or increased among adults aged ≥40 years. We conducted a topical review of surveillance strategies that will be critical to support the elimination of hepatitis B as a public health threat in the United States. In 2019, notifiable disease surveillance for acute hepatitis B showed continued transmission, especially among people who inject drugs and people with multiple sexual partners; rates were highest among people who were aged 30-59 years, non-Hispanic White, and living in rural areas. In contrast, newly reported cases of chronic hepatitis B (CHB) were highest among people who were aged 30-49 years, Asian or Pacific Islander, and living in urban areas. The National Health and Nutrition Examination Survey documented the highest CHB prevalence among non-US-born, non-Hispanic Asian people during 2013-2018; only one-third of people with CHB were aware of their infection. In the context of universal adult vaccination (2022) and screening (2023) recommendations for hepatitis B, better data are needed to support programmatic strategies to improve (1) vaccination rates among people with behaviors that put them at risk for transmission and (2) screening and linkage to care among non-US-born people. Surveillance for hepatitis B needs to be strengthened throughout the health care and public health systems.

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.

The v-safe after vaccination health checker: Active vaccine safety monitoring during CDC's COVID-19 pandemic response.

The Centers for Disease Control and Prevention (CDC) developed and implemented the v-safe after vaccination health checker (v-safe) to monitor COVID-19 vaccine safety and as an active surveillance supplement to existing CDC vaccine safety monitoring programs. V-safe allows persons who received COVID-19 vaccines to report on post-vaccination experiences and how symptoms affected their health at daily, weekly, and monthly timepoints after vaccination. Text message reminders are sent linking to Internet-based health check-in surveys. Surveys include questions to identify v-safe participants who may be eligible to enroll in a separate pregnancy registry activity that evaluates maternal and infant outcomes in those pregnant at the time of vaccination or receiving vaccine in the periconception period. We describe the development of and enhancements to v-safe, data management, promotion and communication to vaccination sites and partners, publications, strengths and limitations, and implications for future systems. We also describe enrollment in v-safe over time and demographics of persons participating in v-safe during the first year of operation (December 14, 2020 - December 13, 2021). During this time, 9,342,582 persons submitted 131,543,087 v-safe surveys. The majority of participants were female (62.3 %) and non-Hispanic White (61.2 %); median age was 49.0 years. Most participants reported receiving an mRNA COVID-19 vaccine as their first recorded dose (95.0 %). V-safe contributed to CDC's vaccine safety assessments for FDA-authorized COVID-19 vaccines by enabling near real-time reporting of reactogenicity once the COVID-19 vaccination program began in the community, encouraging reports to the Vaccine Adverse Event Reporting System and facilitating enrollment in a large post-vaccination pregnancy registry. Given that v-safe is an integral component of the most comprehensive safety monitoring program in U.S. history, we believe that this approach has promise as a potential application for future pandemic response activities as well as rollout of novel vaccines in a non-pandemic context.

Hepatitis C Virus Testing During Pregnancy After Universal Screening Recommendations.

The study evaluates the effect of the 2020 Centers for Disease Control and Prevention and U.S. Preventive Services Task Force recommendations on hepatitis C virus (HCV) screening among pregnant persons nationally and by health insurance type. The study included 5,048,428 pregnant persons aged 15-44 years with either Medicaid or commercial health insurance who had obstetric panel testing performed by Quest Diagnostics, January 2011-June 2021. Antibody screening for HCV infection increased before and accelerated after the updated recommendations in early 2020. Disparities in HCV testing by health insurance status were substantial over the entire study period. Despite substantial progress in the proportion of pregnant persons screened for HCV infection, current testing rates fall short of universal recommendations.

Timing of Positive Hepatitis C Virus Test Results During and 1 Year Before Pregnancy.

The incidence of hepatitis C virus (HCV) infection in reproductive-aged adults quadrupled during the past decade. Hepatitis C can progress to advanced liver disease and be transmitted perinatally. Highly effective curative hepatitis C treatment is available but is not recommended in pregnancy. Using the Surveillance for Emerging Threats to Mothers and Babies Network, we describe timing of positive RNA testing among pregnant people with HCV (HCV RNA detected during or within one year prior to pregnancy). Four US jurisdictions reported 1161 pregnancies during 2018-2021 among people with hepatitis C: 75.9% were multiparous; and 21.4% had their first peri-pregnancy HCV RNA detected prior to pregnancy, indicating potential missed treatment opportunities to improve maternal health and prevent perinatal transmission.

Kawasaki Disease Following the 13-valent Pneumococcal Conjugate Vaccine and Rotavirus Vaccines.

BACKGROUND: Temporal associations between Kawasaki disease (KD) and childhood vaccines have been reported. Limited data on KD following 13-valent pneumococcal conjugate (PCV13) and rotavirus vaccines are available. METHODS: We conducted a self-controlled risk interval study using Vaccine Safety Datalink electronic health record data to investigate the risk of KD following PCV13 and rotavirus vaccines in children <2 years of age who were born from 2006 to 2017. All hospitalized KD cases identified by International Classification of Diseases diagnosis codes that fell within predefined risk (days 1-28 postvaccination) and control (days 29-56 for doses 1 and 2, and days 43-70 for doses 3 and 4) intervals were confirmed by manual chart review. RESULTS: During the study period, 655 cases of KD were identified by International Classification of Diseases codes. Of these, 97 chart-confirmed cases were within risk or control intervals. In analyses, the age-adjusted relative risk for KD following any dose of PCV13 was 0.75 (95% confidence interval, 0.47-1.21). Similarly, the age-adjusted relative risk for KD following any dose of rotavirus vaccine was 0.66 (95% CI, 0.40-1.09). Overall, there was no evidence of an elevated risk of KD following PCV13 or rotavirus vaccines by dose. In addition, no statistically significant temporal clustering of KD cases was identified during days 1 to 70 postvaccination. CONCLUSIONS: PCV13 and rotavirus vaccination were not associated with an increased risk of KD in children <2 years of age. Our findings provide additional evidence for the overall safety of PCV13 and rotavirus vaccines.

Monitoring the safety of COVID-19 vaccines in pregnancy in the US.

Pregnant persons are at increased risk of severe illness from COVID-19. The first COVID-19 vaccines in the U.S. were authorized for emergency use in December 2020 and pregnant persons were eligible and could get vaccinated despite scarce safety data in this population. To monitor the safety of COVID-19 vaccination during pregnancy, four surveillance systems are used by the Centers for Disease Control and Prevention (CDC). The Vaccine Adverse Event Reporting System is a national, passive system that captures reports of potential adverse events. V-safe is a novel, active system that uses text messaging and web-based surveys to provide health check-ins after vaccination; and enrolls eligible v-safe participants in the v-safe pregnancy registry. The Vaccine Safety Datalink is a collaboration between the CDC and nine integrated health care organizations which performs near-real time surveillance and traditional epidemiologic studies on pregnant vaccine recipients. The CDC is committed to timely and comprehensive monitoring of COVID-19 vaccine safety in pregnancy.

Association of Inadvertent 9-Valent Human Papillomavirus Vaccine in Pregnancy With Spontaneous Abortion and Adverse Birth Outcomes.

Importance: The 9-valent human papillomavirus (9vHPV) vaccine is recommended for individuals through age 26 years and may be administered to women up to age 45 years. Data on 9vHPV vaccine exposures during pregnancy are limited. Objective: To evaluate the associations between 9vHPV vaccine exposures during pregnancy or peripregnancy and selected pregnancy and birth outcomes (spontaneous abortion [SAB], preterm birth, small-for-gestational age [SGA] birth, and major structural birth defect). Design, Setting, and Participants: This cohort study analyzed data from 7 participating health systems in the Vaccine Safety Datalink. The cohort comprised pregnancies among girls and women aged 12 to 28 years that ended between October 26, 2015, and November 15, 2018. Singleton pregnancies that ended in a live birth, stillbirth, or SAB were included. Exposures: Vaccine exposure windows were distal (9vHPV or 4vHPV vaccine administered from 22 to 16 weeks before last menstrual period [LMP]), peripregnancy (9vHPV vaccine administered from 42 days before LMP until LMP), and during pregnancy (9vHPV vaccine administered from LMP to 19 completed weeks' gestation). Primary comparisons were (1) girls and women with 9vHPV vaccine exposures during pregnancy vs those with 4vHPV or 9vHPV distal vaccine exposures, (2) girls and women with vaccine exposures peripregnancy vs those with 4vHPV or 9vHPV distal vaccine exposures, and (3) girls and women with 9vHPV vaccine exposures during pregnancy or peripregnancy vs those with 4vHPV or 9vHPV distal vaccine exposure. Main Outcomes and Measures: Spontaneous abortions were confirmed based on medical record review and adjudication. Preterm and SGA births were identified from electronic health record and birth data. Major structural birth defects were based on diagnostic codes using a validated algorithm. Inverse probability weighting was used to balance the covariates. Time-dependent covariate Cox proportional hazards regression models and Poisson regression were used to estimate the associations between 9vHPV vaccine exposures and pregnancy and birth outcomes. Results: The final cohort included 1493 pregnancies among girls and women with a mean (SD) maternal age of 23.9 (2.9) years. Of these pregnancies, 445 (29.8%) had exposures to the 9vHPV vaccine during pregnancy, 496 (33.2%) had exposures to the 9vHPV vaccine peripregnancy, and 552 (37.0%) had 4vHPV or 9vHPV distal vaccine exposures. The 9vHPV vaccine administered during pregnancy was not associated with increased risk for SAB (hazard ratio, 1.12; 95% CI, 0.66-1.93) compared with distal vaccine exposures. Findings were similar for 9vHPV vaccine exposures peripregnancy (relative risk [RR], 0.72; 95% CI, 0.42-1.24). Among live births (n = 1409), 9vHPV vaccine exposures during pregnancy were not associated with increased risks for preterm birth (RR, 0.73; 95% CI, 0.44-1.20) or SGA birth (RR, 1.31; 95% CI, 0.78-2.20). Results were similar regarding the association between 9vHPV vaccine exposures peripregnancy and preterm birth (RR, 0.72; 95% CI, 0.45-1.17) and SGA birth (RR, 1.10; 95% CI, 0.65-1.88). Birth defects were rare in all exposure groups, occurring in about 1% of live births with available infant data. Conclusions and Relevance: This study found that 9vHPV vaccine exposures during or around the time of pregnancy were uncommon and not associated with SABs or selected adverse birth outcomes. These findings can inform counseling for inadvertent 9vHPV vaccine exposures.

U.S. Population-Based background incidence rates of medical conditions for use in safety assessment of COVID-19 vaccines.

The Coronavirus Disease 2019 (COVID-19) pandemic has had a devastating impact on global health, and has resulted in an unprecedented, international collaborative effort to develop vaccines to control the outbreak, protect human lives, and avoid further social and economic disruption. Mass vaccination campaigns are underway in multiple countries and are expected worldwide once more vaccine becomes available. Some early candidate vaccines use novel platforms, such as mRNA encapsulated in lipid nanoparticles, and relatively new platforms, such as replication-deficient viral vectors. While these new vaccine platforms hold promise, limited safety data in humans are available. Serious health outcomes linked to vaccinations are rare, and some outcomes may occur incidentally in the vaccinated population. Knowledge of background incidence rates of these medical conditions is a critical component of vaccine safety monitoring to aid in the assessment of adverse events temporally associated with vaccination and to put these events into context with what would be expected due to chance alone. A list of 22 potential adverse events of special interest (AESI), including neurologic, autoimmune, and cardiovascular disorders, was compiled by subject matter experts at the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention. The most recently available U.S. background rates for these medical conditions, overall and by age, sex, and race/ethnicity (when available), were sourced from reported statistics (data published by medical panels/ associations or federal government reports), and literature reviews in PubMed. This review provides estimates of background incidence rates for medical conditions that may be monitored or studied as AESI during safety surveillance and research for COVID-19 vaccines and other new vaccines.