Infections with SARS-CoV-2 despite two partial vaccinations protect against serious diseases caused by omicron, delta or other virus variants. But a planned triple vaccination is definitely better. Cross-immunity due to a disease only occurs if the interval between the second vaccination and infection is more than three months, scientists at the Charite University Hospital in Berlin have found out.
The scientific study has now been published in “Emerging Infectious Diseases” (DOI: 10.3201/eid2805.220271), as reported by Deutsches Ärzteblatt on Thursday. “Fully vaccinated individuals develop cross-neutralizing antibodies after infection, similar to those after the third vaccination,” wrote study author Leif-Erik Sander. “But if the breakthrough infection happens very early (less than three months) after vaccination, the boosting effect of the infection is rather weak.”
The scientists led by first author Pinkus Tober-Lau examined the serum of 30 people with breakthrough infections after double vaccination – either with the mRNA vaccine from Biontech/Pfizer or with a vaccination with the vector vaccine from AstraZeneca and then the mRNA vaccine. The neutralizing activity was examined with the original strain of SARS-CoV-2 (Wu01) and with four corona variants (alpha, beta, delta, omicron/BA.1). Double vaccinated persons without later infection served as comparison group. It was found that the twice vaccinated persons with non-omicron breakthrough infection had a significantly higher neutralizing activity against all variants examined than those who had been twice vaccinated but not infected.
“However, the booster effect of non-omicron breakthrough infections was highly variable and correlated strongly with the interval between vaccination and infection,” the scientists wrote. Only when a breakthrough infection occurred more than three months after the third vaccination was the serum neutralizing capacity against Wu01 and Omicron comparable to that after a triple vaccination. This effect was seen after omicron and non-omicron breakthrough infections.
Sander: “This booster effect with the formation of cross-neutralizing antibodies, which can neutralize both omicron and delta and other variants, occurs after triple antigen contact.” In the event of an infection despite two vaccinations, the distance is crucial. However, in contrast to a planned third vaccination, this cannot be influenced.