The UK SIREN Study which started in March 2020 and ran till September 2021 on "The impact of detectable anti SARS-COV2 antibody on the incidence of COVID-19 in healthcare workers" has recently submitted a preprint on Vaccine effectiveness & the Durability of protection.
Methods - We assessed vaccine effectiveness (VE) (up to 10-months after first dose) and infection-acquired immunity by comparing time to PCR-confirmed infection in vaccinated and unvaccinated individuals using a Cox regression-model, adjusted by prior SARS-CoV-2 infection status, vaccine-manufacturer/dosing-interval, demographics and workplace exposures.
Results - Of 35,768 participants, 27% (n=9,488) had a prior SARS-CoV-2 infection. Vaccine coverage was high: 97% had two-doses (79% BNT162b2 long-interval, 8% BNT162b2 short-interval, 8% ChAdOx1). There were 2,747 primary infections and 210 reinfections between 07/12/2020 and 21/09/2021. Adjusted VE (aVE) decreased from 81% (95% CI 68%-89%) 14-73 days after dose-2 to 46% (95% CI 22%-63%) >6-months; with no significant difference for short-interval BNT162b2 but significantly lower aVE (50% (95% CI 18%-70%) 14-73 days after dose-2 from ChAdOx1. Protection from infection-acquired immunity showed evidence of waning in unvaccinated follow-up but remained consistently over 90% in those who received two doses of vaccine, even in those infected over 15-months ago.
Conclusion Two doses of BNT162b2 vaccination induce high short-term protection to SARS-CoV-2 infection, which wanes significantly after six months. Infection-acquired immunity boosted with vaccination remains high over a year after infection. Boosters will be essential to maintain protection in vaccinees who have not had primary infection to reduce infection and transmission in this population.
PS: In short, the findings of the study revealed that vaccination with two doses of BNT162b2, at a short or long-interval, induced high protection against SARS-CoV-2 infection (asymptomatic and symptomatic) in the short term; however, this protection waned after six months, when the SARS-CoV-2 Delta variant became the predominant circulating strain.
The overall protection provided by two doses of ChAdOX1 was considerably lower than that given by BNT162b2. However, infection-acquired immunity boosted with vaccination-induced immunity remained high over a year after infection. Based on these observations, the authors recommend the strategic use of booster vaccines to prevent SARS-CoV-2 infection and transmission in the population.
Methods - We assessed vaccine effectiveness (VE) (up to 10-months after first dose) and infection-acquired immunity by comparing time to PCR-confirmed infection in vaccinated and unvaccinated individuals using a Cox regression-model, adjusted by prior SARS-CoV-2 infection status, vaccine-manufacturer/dosing-interval, demographics and workplace exposures.
Results - Of 35,768 participants, 27% (n=9,488) had a prior SARS-CoV-2 infection. Vaccine coverage was high: 97% had two-doses (79% BNT162b2 long-interval, 8% BNT162b2 short-interval, 8% ChAdOx1). There were 2,747 primary infections and 210 reinfections between 07/12/2020 and 21/09/2021. Adjusted VE (aVE) decreased from 81% (95% CI 68%-89%) 14-73 days after dose-2 to 46% (95% CI 22%-63%) >6-months; with no significant difference for short-interval BNT162b2 but significantly lower aVE (50% (95% CI 18%-70%) 14-73 days after dose-2 from ChAdOx1. Protection from infection-acquired immunity showed evidence of waning in unvaccinated follow-up but remained consistently over 90% in those who received two doses of vaccine, even in those infected over 15-months ago.
Conclusion Two doses of BNT162b2 vaccination induce high short-term protection to SARS-CoV-2 infection, which wanes significantly after six months. Infection-acquired immunity boosted with vaccination remains high over a year after infection. Boosters will be essential to maintain protection in vaccinees who have not had primary infection to reduce infection and transmission in this population.
PS: In short, the findings of the study revealed that vaccination with two doses of BNT162b2, at a short or long-interval, induced high protection against SARS-CoV-2 infection (asymptomatic and symptomatic) in the short term; however, this protection waned after six months, when the SARS-CoV-2 Delta variant became the predominant circulating strain.
The overall protection provided by two doses of ChAdOX1 was considerably lower than that given by BNT162b2. However, infection-acquired immunity boosted with vaccination-induced immunity remained high over a year after infection. Based on these observations, the authors recommend the strategic use of booster vaccines to prevent SARS-CoV-2 infection and transmission in the population.
