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BackgroundRapid antigen (RA) tests are being increasingly employed to detect SARS-CoV-2 infections in quarantine and surveillance. Prior research has focused on RT-PCR testing, a single RA test, or generic diagnostic characteristics of RA tests in assessing testing strategies. MethodsFor 18 RA tests with emergency use authorization from the United States of America FDA and an RT-PCR test, we conducted a comparative analysis of the post-quarantine transmission, the effective reproduction number during serial testing, and the false-positive rates. To quantify the extent of transmission, we developed an analytical mathematical framework informed by COVID-19 infectiousness, test specificity, and temporal diagnostic sensitivity data. ResultsWe demonstrate that the relative effectiveness of RA and RT-PCR tests in reducing post-quarantine transmission depends on the quarantine duration and the turnaround time of testing results. For quarantines of two days or shorter, conducting a RA test on exit from quarantine reduces onward transmission more than a single RT-PCR test (with a 24-h delay) conducted upon exit. Applied to a complementary approach of performing serial testing at a specified frequency paired with isolation of positives, we have shown that RA tests outperform RT-PCR with a 24-h delay. The results from our modeling framework are consistent with quarantine and serial testing data collected from a remote industry setting. ConclusionsThese RA test-specific results are an important component of the tool set for policy decision-making, and demonstrate that judicious selection of an appropriate RA test can supply a viable alternative to RT-PCR in efforts to control the spread of disease. Plain language summaryPrevious research has determined optimal timing for testing in quarantine and the utility of different frequencies of testing for disease surveillance using RT-PCR and generalized rapid antigen tests. However, these strategies can depend on the specific rapid antigen test used. By examining 18 rapid antigen tests, we demonstrate that a single rapid antigen test performs better than RT-PCR when quarantines are two days or less in duration. In the context of disease surveillance, the ability of a rapid antigen test to provide results quickly counteracts its lower sensitivity with potentially more false positives. These analytical results based on highly controlled test validation were consistent with real-world data obtained from quarantine and serial testing in an industrial setting.
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Despite the emergence of highly transmissible variants, the number of cases in NYC has fallen from over 5,500 average daily cases in January, 2020 to less than 350 average daily cases in July, 2021. The impact of vaccination in saving lives and averting hospitalizations in NYC has not been formally investigated yet. We used an age-stratified agent-based model calibrated to COVID-19 transmission and vaccination in NYC to evaluate the impact of the vaccination campaign in suppressing the COVID-19 burden. We found that the vaccination campaign has prevented over 250,000 COVID-19 cases, 44,000 hospitalizations and 8,300 deaths from COVID-19 infection since the start of vaccination through July 1, 2021. Notably, the swift vaccine rollout suppressed another wave of COVID-19 that would have led to sustained increase in cases, hospitalizations and deaths during spring triggered by highly transmissible variants. As the Delta variant sweeps across the city, the findings of this study underscore the urgent need to accelerate vaccination and close the vaccine coverage gaps across the city.
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ImportanceRandomized clinical trials have shown that the COVID-19 vaccines currently approved in the US are highly efficacious. However, more evidence is needed to understand the population-level impact of the US vaccination rollout in the face of the changing landscape of COVID-19 pandemic in the US, including variants with higher transmissibility and immune escape. ObjectiveTo quantify the population-level impact of the US vaccination campaign in averting cases, hospitalizations and deaths from December 12, 2020 to June 28, 2021. DesignAge-stratified agent-based model which included transmission dynamics of the Alpha, Gamma and Delta variants in addition to the original Wuhan-1 variant. SettingOur model was calibrated to COVID-19 outbreak and vaccine rollout in the US. Model predictions were made at the country level. ParticipantsSimulated age-stratified population representing US demographics. Main Outcomes and MeasuresCases, hospitalizations and deaths averted by vaccination against COVID-19 in the US, compared to the counterfactuals of no vaccination and vaccination administered at half the actual pace. ResultsThe swift vaccine rollout in the US curbed a potential resurgence of cases in April 2021, which would have been otherwise fuelled by the Alpha variant. Compared to the scenario without vaccines, we estimated that the actual vaccination program averted more than 26 million cases, 1.2 million hospitalizations and saved 279,000 lives. A vaccination campaign with half the actual rollout rate would have led to an additional 460,000 hospitalizations and 121,000 deaths. Conclusions and RelevanceThe COVID-19 vaccination campaign in the US has had an extraordinary impact on reducing disease burden despite the emergence of highly transmissible variants. These findings highlight that the pace of vaccination was essential for mitigating COVID-19 in the US, and underscore the urgent need to close the vaccine coverage gaps in communities across the country. Key PointsO_ST_ABSQuestionC_ST_ABSHow effective was the United States (US) vaccination campaign in suppressing COVID-19 burden? FindingsThe vaccination campaign was highly effective in curbing the COVID-19 outbreak in the US. We estimated that the vaccine rollout saved over 275,000 lives and averted 1.2 million hospitalizations. MeaningThe swift vaccine rollout in the US averted a remarkable number of cases, hospitalizations and deaths despite the emergence of highly transmissible variants.
