Vaccine effectiveness wanes after three months among care home residents

elderly person receiving a Covid vaccination - Vaccination-acquired immunity against Covid-19 wanes substantially after three months among elderly care home residents, suggesting that regular booster jabs may be needed for this group, according to preliminary findings from the Vivaldi study led by UCL researchers. The study, funded by the UK Health Security Agency  and published on the preprint site medRxiv, looked at data from over 15,000 residents (with a median age of 87) and 19,000 staff at 331 care homes across England from December 2020 to December 2021. The researchers found that two vaccine doses were effective at preventing 85.4% of hospitalisations and 94.4% of deaths among care home residents between two and 12 weeks after the second dose, but that this fell to 54.3% of hospitalisations and 62.89% of deaths at three to seven months after vaccination. Looking at booster jabs given in the autumn, the researchers found they restored powerful short-term immunity, reducing hospitalisations among residents by 89.9% and deaths by 97.5% compared to pre-vaccination levels. However, they cautioned that this protection was likely to wane in a similar way to the protection provided by first and second doses. Professor Laura Shallcross (UCL Institute of Health Informatics), leader of the UCL-led Vivaldi team, 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.