Effectiveness and protection duration of Covid-19 vaccines and previous infection against any SARS-CoV-2 infection in young adults – Nature.com

The selection processes for all analytic populations are illustrated in Figs.S1 and S2. Descriptive characteristics for the final study sample are presented in Table1. A total of 280,223 SARS-CoV-2 tests were conducted on 21,261 individuals during the Fall 2021 follow-up period; average number of SARS-CoV-2 tests per individual during follow-up was 13.18 (SD=4.50). By the end of follow-up, reported proof of full and partial vaccination was 60.1% and 0.5%, respectively; 30.3% of individuals had no record of vaccination or previous SARS-CoV-2 infection. Key differences among unvaccinated individuals relative to (fully) vaccinated individuals include a higher proportion of males (unvaccinated: 56.1%, vaccinated: 43.9%), higher proportion of White non-Hispanic individuals (unvaccinated: 81.6%, vaccinated: 78.4%), higher proportion of non-residential students (unvaccinated: 71.2%, vaccinated: 65.5%), lower proportion with pre-existing condition (unvaccinated: 4.8%, vaccinated: 5.7%), higher proportion using nicotine or other smoking products (unvaccinated: 8.2%, vaccinated: 4.5%), lower number of overall SARS-CoV-2 tests (unvaccinated: 20.58, vaccinated: 26.15), higher proportion with a SARS-CoV-2 infection prior to the Fall 2021 semester (unvaccinated: 22.9%, vaccinated: 20.6%), and a higher proportion with a SARS-CoV-2 infection during the Fall 2021 follow-up period (unvaccinated: 12.7%, vaccinated: 4.1%).

Among vaccinated individuals, key differences between vaccine manufactures (TableS1) include proportion who are male (Ad26.CoV2.S: 61.9%, mRNA-1273: 44.8%, BNT162b2: 40.9%), White non-Hispanic (Ad26.CoV2.S: 83.6%, mRNA-1273: 78.2%, BNT162b2: 77.8%), non-residential status (mRNA-1273: 75.9%, Ad26.CoV2.S: 69.6%, BNT162b2: 58.4%), pre-existing conditions (mRNA-1273: 6.6%, Ad26.CoV2.S: 5.8%, BNT162b2: 5.2%), use of nicotine or other smoking products (Ad26.CoV2.S: 6.2%, mRNA-1273: 5.5%, BNT162b2: 3.7%), total number of SARS-CoV-2 tests (mRNA-1273: 28.18, BNT162b2: 25.13, Ad26.CoV2.S: 24.31), SARS-CoV-2 infection prior to the Fall 2021 semester (Ad26.CoV2.S: 24.1%, mRNA-1273: 20.4%, BNT162b2: 20.2%), and SARS-CoV-2 infection during the Fall 2021 follow-up period (Ad26.CoV2.S: 6.5%, BNT162b2: 4.5%, mRNA-1273: 2.9%).

The results for estimated protection are presented in Table2 and Fig.1. Overall, vaccine protection against any SARS-CoV-2 infection during the 18-week follow-up period was 67.4% (95% CI: 63.7%,70.7%). The mRNA-1273 vaccine had the highest protection (75.4%, 95% CI: 70.5%,79.5%), followed by BNT162b2 (65.7%, 95% CI: 61.1%,69.8%) and Ad26.COV2.S (42.8%, 95% CI: 26.1%,55.8%); statistically significant differences were found between all three vaccine types (mRNA-1273 vs BNT162b2: P=0.001; mRNA-1273 vs Ad26.COV2.S: P<0.001; BNT162b2 vs Ad26.COV2.S: P<0.001). Compared to individuals with no protection (i.e., unvaccinated without a previous SARS-CoV-2 infection), protection against repeat infection for unvaccinated individuals with a previous SARS-CoV-2 infection was 72.9% (95% CI: 66.1%,78.4%). Protection from both vaccination and previous infection was 95.0% (95% CI: 92.1%,96.9%); i.e., vaccination provided a 22.1% increase in protection among previously infected individuals (95% CI: 15.8%,28.7%).

Point estimates (with 95% CIs) of (full) vaccine protection among individuals without a previous SARS-CoV-2 infection, vaccine protection among individuals with a previous SARS-CoV-2 infection, and protection from previous infection only. All estimates of protection are relative to individuals with no protection (unvaccinated without a previous SARS-CoV-2 infection).

To assess sensitivity to missing SARS-CoV-2 infection history, analyses were restricted to individuals who participated in Clemson Universitys Covid-19 surveillance testing since the Fall 2020 semester (N=13,057). Descriptive statistics for this analytic sample are presented in TablesS2 and S3; results are presented in TableS4. Increases in protection were observed for individuals vaccinated with mRNA-1273 (protection: 76.4%, 95% CI: 70.3%,81.3%), BNT162b2 (protection: 68.1%, 95% CI: 61.4%,73.6%), and Ad26.COV2.S (protection: 46.6%, 95% CI: 23.2%,62.8%). Results further excluding individuals vaccinated prior to general eligibility (March 31st, 2021) are provided in TableS5. A mild increase in BNT162b2 effectiveness was observed (protection: 70.0%, 95% CI: 63.1%,75.5%).

The analytic samples for protection against any SARS-CoV-2 infection during the follow-up period between December 28th, 2020 and December 4th, 2021 are presented in TablesS6 and S7, with results presented in TableS8. Moderate increases were observed for BNT162b2 (protection: 69.1%, 95% CI: 62.8%,74.3%), Ad26.CoV2.S (protection: 46.6%, 95% CI: 24.2%,62.4%), and previous SARS-CoV-2 infection (protection: 80.9%, 95% CI: 77.1%,84.0%). A mild increase in protection was observed for BNT162b2 (protection: 70.9%, 95% CI: 64.5%,76.2%) when excluding individuals vaccinated prior to March 31st, 2021 (TableS9).

There was a significant increase in the risk of SARS-CoV-2 infection with each month since full vaccination (i.e., 2weeks past final dose) for mRNA-1273 (HR=1.25, 95% CI: 1.10,1.42), BNT162b2 (HR=1.17, 95% CI: 1.09,1.26), but not Ad26.COV2.S (HR=0.94, 95% CI: 0.81,1.09) or previous SARS-CoV-2 infection (HR=0.94, 95% CI: 0.87,1.02). Estimated protection over time for the mRNA vaccines is displayed in Fig.2. Between 0 to 6 months post- vaccination, estimated protection decreased from 88.9% to 58.3% for mRNA-1273 and from 80.2% to 49.2% for BNT162b2. Between 0 to 6 months post vaccination, estimated decrease in overall mRNA vaccine protection against any SARS-CoV-2 infection was 29.7% (95% CI: 17.9%,41.6%). At 6 months post vaccination, statistically significant differences were not observed between mRNA-1273 and BNT162b2 (P=0.27), mRNA-1273 and Ad26.CoV2.S (P=0.59), and BNT162b2 and Ad26.CoV2.S (P=0.89).

Adjusted estimated vaccine protection (point estimate with 95% CIs) by months since full vaccination for mRNA-1273, BNT162b2, and any mRNA vaccine.

Sensitivity analyses accounting for missing SARS-CoV-2 infection history had a negligible impact on results (TableS10). However, a greater decline was observed when removing individuals vaccinated prior to general eligibility (March 31st, 2021). Estimated hazard ratios for months since vaccination were 1.30 for mRNA-1273 (95% CI: 1.07,1.57) and 1.24 for BNT162b2 (95% CI: 1.07,1.43). Greater declines in mRNA vaccine protection were also observed when restricting the sample to the December 28th, 2020 through December 4th, 2021 follow-up periods (TableS10).

We assess sensitivity to classification of vaccination status by assuming that protection starts at day 7 post vaccination for each dose (as opposed to day 14). In this study, results were not sensitive to the assumption of a 7-day or 14-day period. Estimates of overall protection from vaccination and previous infection are presented in TableS11. Among all estimates, (absolute) differences in protection between 7-day and 14-day classification procedures ranged from 0.0% to 1.2%. Absolute differences in change in monthly SARS-CoV-2 infection risk ranged from 0.00 to 0.02 (TableS12).

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Effectiveness and protection duration of Covid-19 vaccines and previous infection against any SARS-CoV-2 infection in young adults - Nature.com