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Background We conducted a prospective cohort study at Kaiser Permanente Southern California to evaluate the relative vaccine effectiveness (rVE) of a booster dose vs 2-dose primary series of messenger RNA (mRNA)-1273 in immunocompetent individuals. Methods Immunocompetent adults who received a booster dose of mRNA-1273 from October 2021 through December 2021 were matched 1:1 to randomly selected 2-dose mRNA-1273 recipients by age, sex, race/ethnicity, and second-dose date and followed up through January 2022. Cox proportional hazards models were used to estimate adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs), comparing outcomes (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] infection and coronavirus disease 2019 [COVID-19] hospitalization and hospital death) in the booster-dose and 2-dose groups. Adjusted rVE (%) was calculated as (1 − aHR) × 100. aHRs and rVE were also estimated by subgroup and month of follow-up. Results The study included 431 328 booster-dose vaccinated adults matched to 431 328 2-dose vaccinated adults. rVE was 61.3% (95% CI: 60.5%–62.2%) against SARS-CoV-2 infection, 89.0% (86.2%–91.2%) against COVID-19 hospitalization, and 96.0% (68.0%–99.5%) against COVID-19 hospital death. rVE against SARS-CoV-2 infection ranged from 55.6% to 66.7% across all subgroups. rVE against SARS-CoV-2 infection decreased from 67.1% (0 to Conclusions Among immunocompetent adults, the mRNA-1273 booster conferred additional protection against SARS-CoV-2 infection and severe COVID-19 disease compared with the 2-dose mRNA-1273 primary series during periods of Delta and Omicron predominance.

Background As prenatal vaccinations continue to be given more frequently, it is important to assess long-term safety events. We investigated the association between prenatal influenza vaccination or infection and autism spectrum disorder (ASD) in offspring. Methods A retrospective cohort study of mother–child pairs with deliveries between 1 January 2011 and 31 December 2014 at Kaiser Permanente Southern California was performed. Children aged >1 year were followed through 31 December 2018. Maternal influenza vaccination or infection during pregnancy was obtained from electronic health records. ASD was defined by International Classification of Diseases, Ninth or Tenth Revisions, Clinical Modification, codes after age 1 year. Cox proportional hazard models estimated the crude and inverse probability of treatment weighted (IPTW) hazard ratios (HR) for the association between maternal influenza vaccination or infection and ASD. Results There were 84 739 mother–child pairs included in the final analytic sample. Of the 46 257 women vaccinated, 32.4% were vaccinated during the first trimester, 41.8% during the second trimester, and 25.8% during the third trimester. ASD was diagnosed in 1930 (2.3%) children. The IPTW analyses showed no association between prenatal influenza vaccination or infection and ASD in offspring (HR, 1.04; 95% confidence interval [CI], .95–1.13; HR, 1.12; 95% CI, .66–1.89, respectively). Conclusions Prenatal influenza vaccination or infection was not associated with ASD risk in offspring. The findings support recommendations to vaccinate pregnant women to protect themselves and their infants, both of whom are vulnerable to severe morbidity following infection.

Background. Approximately 40% of adults develop invasive cancer during their lifetimes, many of whom require chemotherapy. Herpes zoster (HZ) is common and often severe in patients undergoing chemotherapy, yet there are no data regarding whether these patients retain specific protection against HZ if they had previously re10 ceived zoster vaccine. We conducted a study to determine whether zoster vaccine was effective in patients who subsequently underwent chemotherapy. Methods. The cohort study consisted of Kaiser Permanente Southern California members aged ≥60 years treated with chemotherapy. The exposure variable was receipt of zoster vaccine prior to initiation of chemotherapy. Incident HZ cases were identified using International Classification of Diseases, Ninth Revision diagnostic codes. HZ 15 incidence rates were calculated; hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression models. Results. There were 91 and 583 HZ cases in the vaccinated and unvaccinated cohorts, respectively, yielding an incidence rate of 12.87 (95% CI, 10.48–15.80) vs 22.05 (95% CI, 20.33–23.92) per 1000 person-years. Thirty-month cumulative incidence was 3.28% in the vaccinated group and 5.34% in the unvaccinated group (P< .05). The adjusted 20 HR for HZ was 0.58 (95% CI, .46–.73) and showed no significant variation by age, sex, or race. HZ incidence rates remained increased in the small subgroup of persons receiving zoster vaccine within 60 days before chemotherapy, but this was the only group affected by indication bias. No vaccinated patients underwent hospitalization for HZ, compared with 6 unvaccinated patients. Conclusions. Zoster vaccine continues to protect against HZ if recipients later undergo chemotherapy. Our find25 ings provide an additional rationale for offering zoster vaccine to indicated adults while they are immunocompetent.

BACKGROUND Published data on the safety of tetanus-diphtheria-acellular pertussis vaccine (Tdap) in persons aged ≥65 years are limited. This study aims to examine a large cohort of Tdap users ≥65 years for evidence of increased risk of adverse events following vaccination. METHODS A matched cohort study design and a self-controlled case series (SCCS) design were used. The study population was adults aged ≥65 years who received the Tdap or tetanus and diphtheria (Td) vaccine during 1 January 2006-31 December 2010 at 7 health maintenance organizations in the United States. Seven major groups of prespecified events were identified electronically by diagnostic codes. RESULTS The study included 119 573 Tdap vaccinees and the same number of Td vaccinees. The results indicated that the risk of the prespecified events following Tdap was comparable to that following Td vaccination in this elderly population. There was a small increased rate of codes suggesting medically attended inflammatory or allergic events in 1-6 days following Tdap in the SCCS analysis (incidence rate ratio, 1.59 [95% confidence interval, 1.40-1.81]). CONCLUSION Although there is a small increased risk of medically attended inflammatory or allergic events in 1-6 days following Tdap compared to other time periods, it is no more common than that following Td. This study provides empirical safety data suggesting that immunizing adults aged ≥65 years with Tdap to reduce the risk of pertussis in the elderly and their contacts should not have untoward safety consequences.