key: cord-0995965-4h6fwue1
authors: Donadio, Cristiano; Rainone, Antonio; Gouronnec, Adéline; Belmin, Joël; Lafuente –Lafuente, Carmelo
title: Asymptomatic COVID-19 cases among older patients despite BNT162b2 vaccination: a case series in a geriatric rehabilitation ward during an outbreak.
date: 2021-04-11
journal: J Infect
DOI: 10.1016/j.jinf.2021.04.004
sha: 64206b2782f4351f1aa68d9e85947877908e2dc5
doc_id: 995965
cord_uid: 4h6fwue1

nan

To the editor:

We read with great interest the work of Tré-Hardy et al [1] in your pages, studying antibody response in healthcare workers after one and two doses of SARS-CoV-2 mRNA-1273 vaccine. As with other mRNA vaccines [2] , they found high antibody titers following vaccination, which has been associated with effectiveness in preventing symptomatic disease in clinical trials [3, 4] .

The SARS-CoV-19 pandemic is having a dramatic impact [5] , particularly on the elderly, and there is great hope that vaccination against SARS-CoV-2 will reduce mortality and ease the burden of the disease [6] . However, the impact of vaccination on the spreading of the disease is still not well known [7] . In particular, the effectiveness of vaccines for reducing asymptomatic SARS-CoV-2 infection is unknown. This aspect is important, because asymptomatic infection is a major contributor to viral transmission.

In this regard, we observed four patients who developed asymptomatic SARS-CoV-2 infection despite previous complete vaccination with BNT161b2, an mRNA vaccine. All were inpatients in a 40-bed geriatric rehabilitation ward, where a cluster of B.1.1.7 (VOC-202012/1) variant COVID-19 cases occurred. Over a period of 7 days, eight symptomatic cases happened among patients on this ward (Table 1) , one of them in a vaccinated patient. In addition, seven cases occurred among ward staff. In Four of them had previously completed two doses of BNT161b2 vaccine ( Table 1 ). The characteristics of previously vaccinated patient, four asymptomatic and one with symptoms, are shown in Table 2 .

None of the asymptomatic patients developed any symptom of COVID-19 during the follow-up or had negative outcomes. The patient with symptomatic COVID-19 infection despite previous BNT161b2 vaccination was immunocompromised due to a hematological condition (chronic lymphoid leukemia) and developed a moderate COVID-19 related pneumonia, from which he recovered.

This small case series shows that frail older patients vaccinated with BNT161b2 can develop asymptomatic SARS-CoV-2 infection and thus participate to viral transmission. In fact, it is striking to note that the attack rate was the same between vaccinated and unvaccinated patients (Table 1) , the main difference being that the proportion of asymptomatic cases was much higher between vaccinated patients. This observation, however, was obtained in the context of a COVID-19 outbreak in a geriatric rehabilitation ward. The four patients described here had received a full vaccination with the BNT161b2 vaccine and the delay between their first dose and the outbreak was sufficient to allow a complete immunization. All four were fully asymptomatic at all times, despite being very old, having several comorbidities and being infected by the B.1.1.7 variant, which is associated with a higher risk of severe disease and mortality [8] . Three of them were tested again 12 days after and SARS-CoV-2 was detected in only one patient by RT-PCR in the nasal swabs.

Asymptomatic infection is a matter of concern from the point of view of epidemic control, as they can transmit the virus without being aware [9, 10] 1 case per 1000 workers tested [12] .

The number of patients we report is very small and they occurred in a specific setting, so it is not possible to draw any generalizable conclusion. However, these findings suggest that asymptomatic SARS-CoV-2 infection may be frequent in vaccinated frail older patients, and that the main effect of vaccination in this population might be a decrease of the severity of the disease rather than 

safety and antibody response, after one and two doses of mRNA-1273 in seronegative and seropositive healthcare workers

Safety and Immunogenicity of Two RNA-Based Covid-19 Vaccine Candidates

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine

Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine

Comparing SARS-CoV-2 with SARS-CoV and influenza pandemics

SARS-CoV-2 Vaccination -An ounce (actually, much less) of prevention

Warnings regarding the potential coronavirus disease 2019 (COVID-19) transmission risk: Vaccination is not enough

Risk of mortality in patients infected with SARS-CoV-2 variant of concern 202012/1: matched cohort study

COVID-19: A review on the novel coronavirus disease evolution, transmission, detection, control and prevention. Viruses

The challenge of asymptomatic SARS-CoV-2 transmission in care homes

Impact of the COVID-19 vaccine on asymptomatic infection among patients undergoing pre-procedural COVID-19 molecular screening

BNT162b2 mRNA Covid-19 Vaccine Effectiveness among Health Care Workers

This work has been founded by Assistance Publique -Hôpitaux de Paris (APHP) and Sorbonne Université.