Widespread, long-term herd immunity to COVID-19 will be difficult to achieve if the results of a new study are confirmed. The survey of 365,000 people in England showed the proportion of those testing positive for COVID-19 antibodies fell 26.5% between June 20 and Sept. 28, suggesting "immunity is waning quite rapidly," study author Helen Ward tells the BBC. The study, funded by the UK government, required participants to perform finger-prick tests at home. About 6% showed immunoglobulin G (IgG) antibody responses in June. Three months later, just 4.4% did. People who'd had an asymptomatic COVID-19 infection appeared to lose detectable antibodies sooner than others, reports the Wall Street Journal. Age also played a role. Participants between the ages of 18 to 24 saw a 14.9% decline in antibodies, while those ages 75 and older saw a 29% decline.
The study appears in line with other research suggesting antibodies decrease over time. However, "it is possible that people who had been exposed to the virus were less likely to take part over time, which may have contributed to apparent population antibody waning," researchers note. Their results were published Monday before a peer review process, per CNN, which notes researchers looked only for IgG antibody responses, though "other research teams have found that other types of antibodies may persist longer." These results may mean that people with waning immunity will require booster vaccine doses, study director Paul Elliott tells the BBC. More research is needed to determine if antibodies offer any type of immunity. (This study suggests antibodies hold steady for four months.)