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French study adds evidence about vaccine efficacy in challenging population
A recent outbreak of COVID-19 at a French nursing home shows that even fully vaccinated residents remain vulnerable to illness, according to researchers.
Among 74 residents, 23% contracted SARS-CoV-2, including 14 of the 70 who were fully vaccinated, two partially vaccinated residents, and one who was unvaccinated, reported Joel Belmin, MD, PhD, of the Hopital Charles Foix in Ivry-sur-Seine, and colleagues.
Of 102 healthcare professionals, three of the 34 vaccinated workers contracted SARS-CoV-2 (8.8%), as did nine of 68 unvaccinated workers (13.2%). Overall, five were symptomatic (all in the unvaccinated group) and none had severe disease, the authors wrote in a research letter published in JAMA Network Open.
“Our study’s findings suggest that SARS-CoV-2 vaccination may not be sufficient as the sole means to prevent COVID-19 among [nursing home] residents and that other prevention measures should not be abandoned yet in these settings,” the researchers noted.
Prior research on immunogenicity found low antibody titers in nursing home residents following vaccination, suggesting “the potential for diminished effectiveness in this population,” the authors noted.
With only limited prior data available, “the efficacy and effectiveness of COVID-19 vaccines are not well known in this population,” they said.
From March 19 to April 18, Belmin and colleagues analyzed data from medical records in a French nursing home with 77 beds. The index patient was a resident who contracted COVID-19 from a symptomatic visitor. The authors noted that the patient was asymptomatic at the time of a positive PCR test, developed symptoms 2 days later and was treated with nasal oxygenation, fluid infusion, and anticoagulants.
The nursing home residents received Pfizer’s vaccine (Comirnaty) from January to February, and were considered fully vaccinated if they received the second dose at least 14 days prior to the outbreak.
Over three-fourths of residents were women with a mean age of about 88. Of the 17 fully vaccinated residents with COVID-19, 12 were women.
Interestingly, seven vaccinated residents developed severe disease, but none died, while of the two unvaccinated residents, one contracted COVID-19 and died.
Among the three vaccinated healthcare workers who contracted COVID-19, one was fully vaccinated with Pfizer’s vaccine and the two others were partially vaccinated with AstraZeneca’s.
The analysis had several limitations, Belmin and co-authors acknowledged. Minimal demographic data was provided, without any reported medical history on comorbidities or evidence of preexisting immunosuppression. Older women were overrepresented in this cohort, limiting the generalizability of the findings, they added.
Créditos: Comité científico Covid