Direct and indirect effectiveness of mRNA vaccination against SARS-CoV-2 infection in long-term care facilities in Spain

Abstract

Objectives: To estimate indirect and total (direct plus indirect) effects of COVID-19 vaccination in residents in long-term care facilities (LTCF). Design: Registries-based cohort study including all residents in LTCF 65 years or older offered vaccination between 27 December 2020 and 10 March 2021. Risk of SARS-CoV-2 infection following vaccination was compared with the risk in the same individuals in a period before vaccination. Risk in non-vaccinated was also compared to a period before the vaccination programme to estimate indirect protection. Standardized cumulative risk was computed adjusted by previous documented infection (before the start of follow-up) and daily-varying SARS-CoV-2 incidence and reproductive number. Participants: 573,533 records of 299,209 individuals in the National vaccination registry were selected; 99.0% had received at least 1 vaccine-dos, 99.8% was Pfizer/BioNTech (BNT162b2). Residents mean age was 85.9, 70.9% were females. A previous SARS-CoV-2 infection was found in around 25% and 13% of participants, respectively, at the time of vaccine offer and in the reference period. Main outcome measures: Documented SARS-CoV-2 infection identified in the National COVID-19 laboratory registry. Results: Total VE was 57.2% (95% Confidence Interval: 56.1%-58.3%), and was highest starting 28 days after the first vaccine-dose (proxy of more than 7 days after the second dose) and for individuals naive to SARS-CoV-2 [81.8% (81.0%-82.7%)] compared to those with previous infection [56.8% (47.1%-67.7%)]. Vaccination prevented up to 9.6 (9.3-9.9) cases per 10.000 vaccinated per day; 11.6 (11.3-11.9) if naive vs. 0.8 (0.5-1.0) if previous infection. Indirect protection in the non-vaccinated could only be estimated for naive individuals, at 81.4% (73.3%-90.3%) and up to 12.8 (9.4-16.2) infections prevented per 10.000 indirectly protected per day. Conclusions: Our results confirm the effectiveness of mRNA vaccination in institutionalized elderly population, endorse the policy of universal vaccination in this setting, including in people with previous infection, and suggest that even non-vaccinated individuals benefit from indirect protection.

Two doses of the mRNA BNT162b2 vaccine reduce severe outcomes, viral load and secondary attack rate: evidence from a SARS-CoV-2 Alpha outbreak in a nursing home in Germany, January-March 2021

“…Our VE against infection was lower than in previous studies from similar settings [4], [6], [7]. Since this cohort was PCR-tested every 5-6 days throughout the outbreak, we believe that the risk for missing asymptomatic cases was minimal while in other studies under-ascertainment of asymptomatic infection may have occurred.…”

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

“…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. 15,16 We observed reduced hazards of infection in the immediate post-vaccination period (0-13 days) for ChAdOx1, which cannot be attributed to protective effects of the vaccine but might be because recently vaccinated long-term care facilities were less likely to have ongoing outbreaks of infection. Guidance on risk assessmentbased deferral of vaccination in long-term care facilities with active outbreaks was introduced at the end of December, 2020, 35 and is likely to have disproportionately affected facilities predominantly using ChAdOx1, which was deployed later than BNT162b2.…”

“…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.…”

Efficacy and effectiveness of COVID-19 vaccines against SARS-CoV-2 infection: interim results of a living systematic review, 1 January to 14 May 2021

“…Of the 30 studies, 26 investigated the efficacy/effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infections, based on reports of number of symptomatic and asymptomatic PCR-positive individuals [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][22][23][24][25][26][27][28][29][30][31] (Table 1). Studies were conducted in eight different countries (Denmark (n=1), Israel (n=4), Italy (n=1), Qatar (n=1), Spain (n=2), Sweden (n=1), UK (n=8), US (n=7)) and one study was multi-centric [22].…”