Vaccine effectiveness after 1^st and 2^nd dose of the BNT162b2 mRNA Covid-19 Vaccine in long-term care facility residents and healthcare workers – a Danish cohort study

Abstract

Background At the end of 2020, Denmark launched an immunization program against SARS-CoV-2. The Danish health authorities prioritized persons currently living in long-term care facilities (LTCF residents) and frontline healthcare workers (HCW) as the first receivers of vaccination. Here we present preliminary population based vaccine effectiveness (VE) estimates in these two target groups. Methods The study was designed as a retrospective registry- and population-based observational cohort study including all LTCF residents and all HWC. The outcome was a polymerase chain reaction confirmed SARS-CoV-2, and VE was estimated for different periods following first and second dose. We used Poisson and Cox regressions to estimate respectively crude and calendar time-adjusted VE for the BNT162b2 mRNA Covid-19 Vaccine from Pfizer/BioNTech with 95% confidence intervals (CI) for vaccinated versus unvaccinated. Results A total of 39,040 LTCF residents (median age at first dose; 84 years, Interquartile range (IQR): 77-90) and 331,039 HCW (median age at first dose; 47 years, IQR: 36-57) were included. Among LTCF residents, 95.2% and 86.0% received first and second dose from 27 December 2020 until 18 February 2021, for HWC the proportion was 27.8% and 24.4%. During a median follow-up of 53 days , there were 488 and 5,663 confirmed SARS-CoV-2 cases in the unvaccinated groups, whereas there were 57 and 52 in LTCF residents and HCW within the first 7 days after the second dose and 27 and 10 cases beyond seven days of second dose. No protective effect was observed for LTCF residents after first dose. In HCW, VE was 17% (95% CI; 4-28) in the > 14 days after first dose (before second dose). Furthermore, the VE in LTCF residents at day 0-7 of second dose was 52% (95% CI; 27-69) and 46% (95% CI; 28-59) in HCW. Beyond seven days of second dose, VE increased to 64% (95% CI; 14-84) and 90% (95% CI; 82-95) in the two groups, respectively. Conclusion The results were promising regarding the VE both within and beyond seven days of second vaccination with the BNT162b2 mRNA Covid-19 Vaccine currently used in many countries to help mitigate the global SARS-CoV-2 pandemic. Impact of the research: So far, observational studies of the real-word effectiveness of the mRNA Vaccine BNT162b2 has been limited to the period after the administration of the first dose. This is the first report to date to present vaccine effectiveness (VE) estimates after the second BNT162b2 mRNA Covid-19 Vaccine. We estimated a VE of 52% and 46% in LTCF residents and HCW within seven days, which increased to 64% and 90% in the two groups respectively beyond seven days of immunization. These findings supports maintaining a two-dose schedule of the BNT162b2 mRNA Covid-19 Vaccine.

Vaccine effectiveness of the first dose of ChAdOx1 nCoV-19 and BNT162b2 against SARS-CoV-2 infection in residents of long-term care facilities in England (VIVALDI): a prospective cohort study

“…Although we found no additional benefit of vaccination in residents with previous natural infection, it remains important to examine the additional benefits provided to older adults by a second dose of vaccine, particularly in the context of new variants of concern, for which immunological data suggest the importance of a second inoculation. [32][33][34] Data from a Danish observational study in long-term care facility residents suggest that a single dose of BNT162b2 is ineffective in preventing infection; 13 however, participants received the second vaccine dose a median of 24 days after the first dose, which, based on our findings, is probably too short a period to capture the protective effects of a single vaccine dose. Two large Spanish studies in longterm care facility residents reported similar single-dose BNT162b2 vaccine effective ness estimates to those reported here; however, these studies have limitations of shorter dosing intervals than used in the UK setting and little or no routine asymptomatic screening.…”

“…6 Consequently, trial estimates of vaccine efficacy might not be generalisable to long-term care facility residents because of age-related differences in vaccine-induced immune responses. [7][8][9] Observational data from post-licensure studies in older adults are emerging, [10][11][12] and although a small number of preprint articles have reported on populations in long-term care facilities, [13][14][15][16] the study populations were exclusively vaccinated with BNT162b2 at the manufacturer-recommended dosing interval, and regular asymptomatic screening was rarely done.…”

Vaccine effectiveness of the BNT162b2 mRNA COVID-19 vaccine against RT-PCR confirmed SARS-CoV-2 infections, hospitalisations and mortality in prioritised risk groups

“…The first priority groups for vaccinations were residents in long-term care facilities (LTCF) and frontline healthcare workers (HCW). Seven days after the second dose the preliminary vaccine effectiveness (VE) estimates in preventing SARS-CoV-2 infections were 64% (95% confidence interval (CI); 14-84) and 90% (95% CI; 82-95) in these two groups, respectively [2].…”

Outbreak of SARS-CoV-2 Lineage 20I/501Y.V1 in a Nursing Home Underlines the Crucial Role of Vaccination in Both Residents and Staff

“…Few data on the effectiveness of SARS-CoV-2 vaccines in LTCF residents are available up to date. In a Danish cohort study [26], the adjusted effectiveness against both symptomatic and asymptomatic cases in LTCF residents (n = 39,040; mean age 84 years)…”

“…In a Danish cohort study [26], the adjusted effectiveness against both symptomatic and asymptomatic cases in LTCF residents (n = 39,040; mean age 84 years) was 52% (95% CI: 27-69%) and 64% (95% CI: 14-84%) during the periods of 0-7 and >7 days after the second dose, respectively. Although the present report was not designed nor powered to estimate vaccine effectiveness, the vaccination failure rate against any (asymptomatic or symptomatic) RT-PCR-confirmed infection observed is consistent with the findings of the Danish study [26]. In a recent US study [27], the incidence of SARS-CoV-2 in vaccinated (n = 13,048) LTCF residents was 1.0% within 2 weeks after receipt of the second dose.…”