Cases of COVID-19 reported including deaths in care home residents after full-course vaccination
Simon Collins, HIV i-Base
Several recent studies have reported cases of COVID-19 in residential care homes despite full-course mRNA vaccination, including the B.1.351 variant. [1, 2]
Other studies have also reported significantly lower humoral responses to COVID-19 vaccines in some people with reduced immune function, including those older than 80 years. 
A paper published in CID reported an outbreak of the 501.v2 (B.1.351; South African) variant in an elderly nursing home in France. All non-vaccinated residents (5/5) became infected compared to half (13/26) who had been fully vaccinated (two doses) with the Pfizer mRNA vaccine (BNT162b2). COVID-19 was serious in 4/5 and 2/13 of these two groups respectively. 
This study included 31 residents and 59 staff. The first case was in a 92 year-old resident, with 17 residents testing positive over the next three weeks. Vaccinated residents had received their second vaccine dose from 4 to 26 February,
Only 19/59 staff were fully vaccinated. with 1/19 becoming infected vs 10/40 unvaccinated staff. No staff developed serious COVID-19 symptoms but the outcomes for residents who had received two vaccine doses was more serious.
Although 2/13 cases were asymptomatic, 9/13 developed mild to moderate symptoms and 2/13 2 (15.4%) progressed to severe disease and died, secondary to acute respiratory distress syndrome (ARDS).
A second more optimistic but still cautious study included a retrospective review from 280 care homes in the US reported in a letter to the NEJM. This included more than 18,000 vaccinated (13,000 of which had received both doses) and approximately 4,000 unvaccinated residents. 
The incidence of infections declined significantly over time in all groups. Vaccination were mRNA: 80% Pfizer, 20% Moderna.
In those receiving one dose there were 822 incident cases (4.5%) within 0 to 14 days and 250 cases (1.4%) at 15 to 28 days. In those who received both doses there were 130 incident cases (1.0%) within 0 to 14 days and 38 cases (0.3%) after 14 days. Cases also decreased in unvaccinated residents from 173 cases (4.3%) within 0 to 14 days after the first vaccination clinic to 12 cases (0.3%) at more than 42 days after the clinic.
While showing levels of community protection in those who were unvaccinated, the paper showed infections after receiving both doses.
These data should inform individual management of risk for care home residents.
They also highlight the continued risk to residents if staff are not vaccinated, including vulnerability to new variants.
- Bailly B et al, BNT162b2 mRNA vaccination did not prevent an outbreak of SARS COV-2 variant 501Y.V2 in an elderly nursing home but reduced transmission and disease severity. Clinical Infectious Diseases, ciab446. DOI: 10.1093/cid/ciab446. (16 May 2021).
- White EM et al. Incident SARS-CoV-2 Infection among mRNA-Vaccinated and Unvaccinated Nursing Home Residents. NEJM. DOI: 10.1056/NEJMc2104849. (19 May 2021).
- Collins S. Low responses to mRNA COVID-19 vaccines in those older than 80 vs <60 years and in recipients of solid organ transplants. HTB (3 May 2021).