3rd vaccination is better than two vaccinations plus an infection

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Infection with SARS-CoV-2, despite having completed two partial vaccinations, protects against severe illness caused by omicron, delta, or other virus variants. But a planned triple vaccination is better. Scientists at the Charite University Hospital in Berlin have found that cross-immunity from disease only occurs if there are more than three months between the second vaccination and the infection.

The scientific study has now been published in “Emerging Infectious Diseases” (DOI: 10.3201/eid2805.220271), as reported by the German Medical Journal on Thursday. “Fully vaccinated individuals form cross-neutralizing antibodies after infection, similar to those after the third vaccination,” study author Leif-Erik Sander wrote. “But if the breakthrough infection happens very early (less than three months) after vaccination, the booster effect of infection is rather weak.”

Serum from 30 people with breakthrough infections studied

The scientists led by first author Pinkus Tober-Lau examined the serum of 30 people with breakthrough infections after two vaccinations – either with the mRNA vaccine from Biontech/Pfizer or with vaccination with the vector vaccine from AstraZeneca and then the mRNA vaccine.

Different reactions

The neutralizing activity was investigated with the original strain of SARS-CoV-2 (Wu01) and with four corona variants (alpha, beta, delta, omicron/BA.1). Twice-vaccinated individuals without subsequent infection served as a comparison group. This showed that the twice-vaccinated persons with non-omicron breakthrough infection had a significantly higher neutralizing activity against all variants investigated than those who had been twice-vaccinated but not infected.

“However, the booster effect of non-omicron breakthrough infections was highly variable and strongly correlated with the interval between vaccination and infection,” the scientists wrote. The neutralizing capacity of serum against Wu01 and omicron comparable to that after triple vaccination occurred only when breakthrough infection occurred more than three months after the third vaccination. This effect was observed after omicron and non-omicron breakthrough infections.