Long-term Effects of SARS-CoV-2 Vaccination in the Nursing Home Setting

Giulia Rivasi MD; Matteo Bulgaresi MD; Chiara Bandinelli MD; Daniela Balzi BSc; Francesca Tarantini PhD; Silvia Tognelli MD; Chiara Lorini PhD; Primo Buscemi MD; Lorenzo Baggiani MD; Giancarlo Landini MD; Andrea Ungar PhD; Guglielmo Bonaccorsi MD; Enrico Mossello PhD; Enrico Benvenuti MD

Disclosures

J Am Geriatr Soc. 2022;70(5):1336-1341. 

In This Article

Abstract and Introduction

Abstract

Background: SARS-CoV-2 vaccination has significantly reduced infection, hospitalization, and lethality rates among nursing home (NH) residents, but durability of vaccine effects remains unknown.

This study investigated the long-term impact of BNT162b2 SARS-CoV-2 vaccine on breakthrough infection rates in the NHs of Florence, Italy.

Methods: Participants included residents living in Florence NHs as of April 1st, 2021, who had completed the primary SARS-CoV2 vaccination course by February 15th, 2021. Weekly rates of breakthrough infection were calculated between April 1st and October 31st 2021, with 7-day incidence defined as the number of new confirmed SARS-CoV-2-positive residents over the vaccinated resident census. Hospital admissions and deaths were recorded from local administrative and clinical sources. Patients admitted to NHs after April 1st were excluded to avoid confounding effect of different vaccination timing.

Results: Among 2271 vaccinated residents (mean age 86.6, 74% female), we recorded 105 cases of breakthrough infections. Rates of breakthrough infection remained very low in the 6 months after vaccination, but started to rise over the following months, peaking at 0.94%, and then became stable around 0.2%–0.3%. Over the study period, infection rates remained low as compared to the incidence of SARS-CoV-2 infection during pre-vaccination period. Overall hospitalization and lethality rates were 8%.

Conclusions: Among vaccinated NH residents, rates of breakthrough SARS-CoV-2 infection, hospitalization and lethality remained low up to 9 months following primary vaccination course. A mild resurgence of SARS-CoV-2 infection, after 6 months from vaccination, suggests a decline of vaccine effectiveness in preventing transmission.

Introduction

The BNT162b2 mRNA vaccine has proven effective in preventing new SARS-CoV-2 infections and severe COVID-19 disease, with protective effect becoming evident from 2 weeks after the first dose.[1] What remains unclear, however, is how long the vaccine provides protection against COVID-19 and against SARS-CoV-2 transmission.

A recent update to the preliminary efficacy report of the BNT162b2 described a gradual decline of vaccine efficacy in disease prevention over the 6 months following vaccination, with an average 6% reduction of efficacy, every 2 months.[2] Moreover, available data indicate that the immune response to the BNT162b2 vaccine declines over time after vaccination in all individuals, reaching lower antibody levels among older in comparison with younger adults.[3–5] These findings raise a concern that, in the upcoming months, a large proportion of vaccinated individuals could lose their protection against SARS-CoV-2 infection, potentially increasing the risk for new epidemic waves. Indeed, recent reports confirm that BNT162b2 effectiveness against infection decreases over time and describe an increase of SARS-CoV-2 cases in fully vaccinated persons (i.e., breakthrough infections), in parallel with the circulation of SARS-CoV-2 variant strains.[4,6–8]

The issue is even more relevant to nursing home (NH) residents, a vulnerable population characterized by higher risk for severe COVID-19 outcomes[9–11] and blunted immune response to the BNT162b2 vaccine.[12,13] Studies have clearly demonstrated that SARS-CoV-2 vaccination had a positive impact on the epidemic course, hospital admissions and death risk among NH residents[11,14–16] although a decline of effectiveness against SARS-CoV-2 infection has been observed in this population after Delta variant diffusion.[7] Understanding the long-term effectiveness of vaccination is a necessary prerequisite to develop appropriate preventive healthcare strategies, particularly in subgroups at higher risk of COVID-19-related adverse outcomes such as NH residents.

The present study investigated the long-term impact of BNT162b2 SARS-CoV-2 vaccine on breakthrough infection rates in residents of Florence NHs (Tuscany, Italy).

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