Those who are vaccinated against COVID-19 and have been infected have a very high level of protection against hospitalization and severe disease a year after their most recent infection or shot, according to a new analysis led by the World Health Organization.
Hybrid immunity – the mix of protection provided by COVID-19 vaccination as well as infection – was over 97% effective at preventing hospitalization and severe COVID-19 among fully vaccinated individuals a year after their most recent infection or vaccination, according to the analysis published in The Lancet Infectious Diseases on Wednesday.
Protection against infection, however, waned to nearly 42% a year after developing hybrid immunity for those with a primary vaccination series, the analysis of more than two dozen studies found. Those who got a COVID-19 booster shot as well had more than 46% effectiveness against infection six months after the shot.
The analysis also looked at unvaccinated individuals who were infected with COVID-19 and found that their protection against hospitalization and severe COVID-19 also remained relatively high one year after infection, while protection against infection also waned. For those with previous infection and no vaccinations, effectiveness against hospitalization and severe disease was nearly 75% a year out, while protection against infection was less than 25%.
“The analysis shows that hybrid immunity provides higher protection, demonstrating the advantages of vaccination even after people have had COVID-19,” WHO said in a statement.
The analysis suggested that such data could be used to tailor booster shot guidance, adding that booster campaigns could be timed before an expected surge in COVID-19 activity.
“Individuals with hybrid immunity had the highest magnitude and durability of protection, and as a result might be able to extend the period before booster vaccinations are needed compared to individuals who have never been infected,” the analysis said.
It said that “given the waning protection for both infection-induced and vaccine-induced immunity against SARS-CoV-2 infection or reinfection, wider vaccination among populations could be timed for rollout before periods of expected increased incidence, such as the winter season.”
Additionally, the analysis suggested that a six-month delay for the booster dose “might be justified after the last infection or vaccination for individuals with a known history of previous infection and full primary series vaccination.”
The data comes as the Food and Drug Administration’s committee of outside vaccine experts are set to talk about the COVID-19 booster strategy next week.
“Since the initial authorizations of these vaccines, we have learned that protection wanes over time, especially as the virus rapidly mutates and new variants and subvariants emerge,” FDA’s Peter Marks said in a statement announcing the meeting on Jan. 26. “Therefore, it’s important to continue discussions about the optimal composition of COVID-19 vaccines for primary and booster vaccination, as well as the optimal interval for booster vaccination.”
The Biden administration has already floated the idea of an annual COVID-19 booster, but such a plan still faces many questions, including what the makeup of the shot should be and when it should be offered.