Vaccination-acquired immunity against Covid-19 significantly wanes after three months among elderly care home residents, indicating that regular booster jabs may be required for this “vulnerable” group, according to preliminary findings from the Vivaldi study led by UCL researchers.
Over than 15,000 care home residents were surveyed in 331 care homes across England between December 2020 and December 2021, with the results revealing that protection against hospitalisation and death fell by one-third three to seven months after vaccination.
The researchers found that two vaccine doses were effective at preventing 85% of hospitalisations and 94% of deaths among care home residents between two and 12 weeks after the second dose, but this protection fell to 54% of hospitalisations and 63% of deaths in the following four months.
Of 19,000 care home staff, with an average age of 45, who were also tracked in the study, protection against infection fell marginally from 50% to 42% reduced risk after three months and there appeared to be no substantial waning in immunity against severe disease, with very few hospitalisations occurring after vaccination.
Professor Laura Shallcross, public health expert at University College London and author of the paper, 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.
“We observe an increased risk of infection, hospital admission and death in residents as early as 12 weeks following vaccination. 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.
“Our data stops before Omicron became dominant, but it is likely this pattern of diminishing immunity after vaccination will continue with this milder variant.”
Professor Shallcross added that “annual boosters may not be enough”. A second booster (fourth dose), is being offered from April to adults aged 75 and over and residents in care homes, with the potential for further boosters to be rolled out in the autumn, depending on advice from the Joint Committee on Vaccination and Immunisation (JCVI).
“A booster every six months, based on our data, is not unreasonable,” she said, adding that it may make sense to give people an autumn booster ahead of a winter surge, as with flu. However, epidemiologists predict that Covid-19 will not settle into a regular seasonal pattern in the next year or two, with a likelihood of erratic spring and summer waves of infection.
Shallcross also raised concerns that elderly people in the community might underestimate their continued risk from Covid-19, particularly since government messaging has stressed the need to get back to normal. “People might think they’re protected and not get the next dose, but they might not be as protected as they think,” she said.
From April, a second booster (fourth dose), is being offered to adults aged 75 and over and residents in care homes. Further boosters could be rolled out in the autumn, depending on advice from the Joint Committee on Vaccination and Immunisation (JCVI), the health secretary, Sajid Javid said earlier this week.