A growing body of research on residents of long-term care facilities is helping to fill a large evidence gap regarding the effectiveness of COVID-19 vaccinations in this population, say investigators from the London School of Economics and Political Science.

COVID-19 vaccine trials systematically excluded the frail and elderly. But there now are enough recent, original studies in the U.S. and internationally to begin understanding the outcomes of vaccination campaigns, the researchers wrote in the Journal of the American Medical Directors Association

In a comprehensive evidence summary, first author Maximilian Salcher-Konrad and colleagues found studies that addressed vaccine efficacy at the individual and facility levels, and that documented immune response.

Among the findings:

  • Two studies found statistically significant lower rates of new infections among residents of LTC facilities in the 40 weeks following the start of vaccination drives compared to what would be expected without vaccinations. Evidence of the impact on death rates was less consistent.
  • One study found decreased risk of infections once 50% of residents in a facility had received their first dose, with varying effects over time.
  • A Spanish study estimated COVID-19 infections and deaths were reduced by three-quarters once 70% of LTC residents were fully vaccinated.
  • Three studies from the U.S., Germany, and Northern Ireland, reported substantial outbreaks despite high first-dose vaccination rates of residents, with attack rates between 18% and 34% in affected facilities. 
  • Potential for breakthrough infections in fully vaccinated residents was reported in studies from the U.S. and Northern Ireland. Viral load in vaccinated, infected residents may be smaller compared to unvaccinated residents, they found.
  • Five studies consistently showed higher immune response — antibody levels — in residents with prior infections. In residents without prior infections, immune response may be insufficient for approximately half of residents after the first dose, and for some even after the second dose, researchers discovered. 
  • Residents with prior infection also had higher antibody levels after the second dose, but other characteristics (including frailty and cognitive impairment) were not associated with different antibody levels. 

The uptake of vaccines among LTC staff was not addressed in the evidence summary, and the authors acknowledged that this is a key issue in achieving high levels of protection against COVID-19.