Your browser doesn't support javascript.
Montrer: 20 | 50 | 100
Résultats 1 - 2 de 2
Ajouter des filtres

Base de données
Les sujets
Type de document
Gamme d'année
Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-22275958


Concerns about the duration of protection conferred by COVID-19 vaccines have arisen in postlicensure evaluations. However, "depletion of susceptibles" bias driven by differential accrual of infection among vaccinated and unvaccinated individuals may contribute to the appearance of waning vaccine effectiveness (VE) in epidemiologic studies, potentially hindering interpretation of estimates. We enrolled California residents who received molecular SARS-CoV-2 tests in a matched, test-negative design case-control study to estimate VE of mRNA-based COVID-19 vaccines between 23 February and 5 December 2021. We analyzed waning protection following 2 vaccine doses using conditional logistic regression models. Additionally, we used data from case-based surveillance along with estimated case-to-infection ratios from a population-based serological study to quantify the potential contribution of the "depletion-of-susceptibles" bias to time-varying VE estimates for 2 doses. We also estimated VE for 3 doses relative to 0 doses and 2 doses, by time since second dose receipt. Pooled VE of BNT162b2 and mRNA-1273 against symptomatic SARS-CoV-2 infection was 91.3% (95% confidence interval: 83.8-95.4%) at 14 days after second-dose receipt and declined to 50.8% (31.2-75.6%) at 7 months. Accounting for differential depletion-of-susceptibles among vaccinated and unvaccinated individuals, we estimated VE was 53.2% (23.6-71.2%) at 7 months among individuals who had completed the primary series (2 doses). With receipt of a third dose of BN162b2 or mRNA-1273, VE increased to 95.0% (82.8-98.6%), compared with zero doses. These findings confirm that observed waning of protection is not attributable to epidemiologic bias and support ongoing efforts to administer additional vaccine doses to mitigate burden of COVID-19.

Preprint Dans Anglais | medRxiv | ID: ppmedrxiv-21267565


ImportanceUnderstanding how SARS-CoV-2 seroprevalence varies regionally across California is critical to the public health response to the pandemic. ObjectiveTo estimate how many Californians have antibodies against SARS-CoV-2 from prior infection or vaccination. DesignWave 1 of CalScope: a repeated cross-sectional serosurvey of adults and children enrolled between April 20, 2021 and June 16, 2021. SettingA population-based random sample of households in seven counties in California (Alameda, El Dorado, Kern, Los Angeles, Monterey, San Diego, and Shasta) were invited to complete an at-home SARS-CoV-2 antibody test and survey instrument. ParticipantsInvitations were sent to 200,000 randomly selected households in the seven counties. From each household, 1 adult (18 years and older) and 1 child (aged 6 months to 17 years) could enroll in the study. There were no exclusion criteria. Main Outcome(s) and MeasuresAll specimens were tested for antibodies against the nucleocapsid and spike proteins of SARS-CoV-2. The primary outcome was serostatus category, which was determined based on antibody test results and self-reported vaccination status: seronegative, antibodies from infection only, antibodies from infection and vaccination, and antibodies from vaccination alone. We used inverse probability of selection weights and iterative proportional fitting to account for non-response. Results11,161 households enrolled in wave 1 of CalScope, with 7,483 adults and 1,375 children completing antibody testing. As of June 2021, 27% (95%CI [23%, 31%]) of adults and 30% (95%CI [24%, 36%]) of children had evidence of prior SARS-CoV-2 infection; 33% (95%CI [28%, 37%]) of adults and 57% (95%CI [48%, 66%]) of children were seronegative. Serostatus varied regionally. Californians 65 years or older were most likely to have antibodies from vaccine alone (59%; 95%CI [48%, 69%]) and children between 5-11 years old were most likely to have antibodies from prior infection alone (36%; 95%CI [21%, 52%]). Conclusions and RelevanceAs of June 2021, a third of adults in California and most children under 18 remained seronegative. Seroprevalence varied regionally and by demographic group, suggesting that some regions or populations might remain more vulnerable to subsequent surges than others. Key PointsO_ST_ABSQuestionC_ST_ABSWhat is the prevalence of vaccine and infection derived antibodies against SARS-CoV-2 in adults and children in California? FindingsIn this population-based serosurvey that included 11,161 households, as of June 2021, 33% of adults and 57% of children were seronegative; 18% of adults and 26% of children had antibodies from infection alone; 9% of adults and 5% of children had antibodies from both infection and vaccination; and 41% of adults and 13% of children had antibodies from vaccination alone. MeaningSerostatus varied considerably across geographic regions, suggesting that certain areas might be at increased risk for future COVID-19 surges.

Détails de la recherche