A nursing home resident receives a booster shot
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Repeat COVID-19 booster shots may be needed to offer ongoing protection from COVID-19 to vulnerable nursing home residents, a study across hundreds of facilities indicates.

The ongoing Vivaldi nursing home study, launched in the United Kingdom in June 2020, includes a one-year follow-up of immunity to SARS-CoV-2, the longest such study so far in this cohort, investigators say. Researchers examined national data from PCR testing done two to three times a month, as well as hospitalization and death data. 

The new results, which have yet to be peer reviewed, reveal that boosters are valuable, even if they need to be repeated, the researchers asserted. Test results showed that vaccine-derived immunity fell substantially three months after vaccination among the residents and staff of 331 nursing homes, they reported.

After a two-dose initial vaccination, residents’ protection against hospitalization fell from 85% at 12 weeks to 54% by three months, for example. Efficacy against mortality fell from 94% to 63%. Results were similar, whether the residents received the Pfizer or Moderna mRNA vaccines or the U.K.-approved AstraZeneca vaccine.

Boosters work — but for how long?

Subsequent booster shots reestablished strong immunity, but this protection was likely to fade just as it had after the initial series of shots, according to Laura Shallcross Ph.D., of University College London in the United Kingdom. The results not only demonstrate the value of booster vaccinations, but that there may be an ongoing need for additional shots, she said.

“Our data suggests that repeated booster jabs may be needed to protect elderly care home residents in future, as immunity wanes relatively quickly in this group following vaccination,” Shallcross said.

Care providers should keep an eye on vaccine efficacy in this setting, she added.

“This underscores the critical need for continued surveillance in care homes to provide an early warning of surges in infection linked to new variants or waning immunity,” she said.

Although the study used older data when earlier variants dominated, investigators expect vaccination immunity to follow the same course in the omicron era. Studies in the United States, meanwhile, also have shown relatively short-lived mRNA vaccine efficacy and the importance of booster shots in restoring immunity. 

Booster uptake has lagged in most U.S. nursing homes, despite numerous pleas from federal health officials, as McKnight’s Clinical Daily has previously reported.  

The current study’s participants included 15,000 residents with a median age of 87 and 19,000 staff.  Full findings were published on the preprint server medRxiv.