ABSTRACT
BackgroundWe estimated SARS-CoV-2 Delta and Omicron-specific effectiveness of 2 and 3 mRNA COVID-19 vaccine doses in adults against symptomatic illness in US outpatient settings. MethodsBetween October 1, 2021, and February 12, 2022, research staff consented and enrolled eligible participants who had fever, cough, or loss of taste or smell and sought outpatient medical care or clinical SARS-CoV-2 testing within 10 days of illness onset. Using the test-negative design, we compared the odds of receiving 2 or 3 mRNA COVID-19 vaccine doses among SARS-CoV-2 cases versus controls using logistic regression. Regression models were adjusted for study site, age, onset week, and prior SARS-CoV-2 infection. Vaccine effectiveness (VE) was calculated as (1 - adjusted odds ratio) x 100%. ResultsAmong 3847 participants included for analysis, 574 (32%) of 1775 tested positive for SARS-CoV-2 during the Delta predominant period and 1006 (56%) of 1794 participants tested positive during the Omicron predominant period. When Delta predominated, VE against symptomatic illness in outpatient settings was 63% (95% CI: 51% to 72%) among mRNA 2-dose recipients and 96% (95% CI: 93% to 98%) for 3-dose recipients. When Omicron predominated, VE was 21% (95% CI: -6% to 41%) among 2-dose recipients and 62% (95% CI: 48% to 72%) among 3-dose recipients. ConclusionsIn this adult population, 3 mRNA COVID-19 vaccine doses provided substantial protection against symptomatic illness in outpatient settings when the Omicron variant became the predominant cause of COVID-19 in the U.S. These findings support the recommendation for a 3rd mRNA COVID-19 vaccine dose.
ABSTRACT
IntroductoryThe evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in the emergence of many new variant lineages that have exacerbated the COVID-19 pandemic. Some of those variants were designated as variants of concern/interest (VOC/VOI) by national or international authorities based on many factors including their potential impact on vaccines. To ascertain and rank the risk of VOCs and VOIs, we analyzed their ability to escape from vaccine-induced antibodies. The variants showed differential reductions in neutralization and replication titers by post-vaccination sera. Although the Omicron variant showed the most escape from neutralization, sera collected after a third dose of vaccine (booster sera) retained moderate neutralizing activity against that variant. Therefore, vaccination remains the most effective strategy to combat the COVID-19 pandemic.
ABSTRACT
Case-based tracking of COVID-19 in children and adolescents may underestimate infection, and compared with adults there is little pediatric SARS-CoV-2 seroprevalence data. To assess evidence of previous SARS-CoV-2 infections among children and adolescents in Mississippi, serologic testing for antibodies to SARS-CoV-2 was conducted on a convenience sample of residual serum specimens collected for routine laboratory testing by an academic medical center laboratory during May 17 through September 19, 2020. Seroprevalence by calendar month was standardized to the state population by race/ethnicity; cumulative numbers of infections were estimated by extrapolating seroprevalence to all those aged <18 years in Mississippi. Serum specimens from 1,603 individuals were tested; 175 (10.9%) were positive for SARS-CoV-2 antibodies. Among 1,579 (98.5%) individuals for whom race/ethnicity was known, the number testing positive was 16 (23.2%) of 69 Hispanic individuals, 117 (13.0%) of 901 non-Hispanic Black individuals and 30 (5.3%) of 565 non-Hispanic White individuals. Population-weighted seroprevalence estimates among those aged <18 years increased from 2.6% in May to 16.9% in September 2020. Cumulative numbers of infections extrapolated from seroprevalence data, however, were estimated at 117,805 (95% confidence interval [CI] = 68,771-168,708), suggesting that cases in children and adolescents are much higher than what was reported to the Mississippi State Department of Health (9,044 cases during this period). Further data to appreciate the burden of pediatric disease to inform public health policy is urgently needed.
ABSTRACT
We compared symptoms and characteristics of 4961 ambulatory patients with and without laboratory-confirmed SARS-CoV-2 infection. Findings indicate that clinical symptoms alone would be insufficient to distinguish between COVID-19 and other respiratory infections (e.g., influenza) and/or to evaluate the effects of preventive interventions (e.g., vaccinations).
