Vaccination may protect against severe Covid-19 for 3 years

The task force estimates that mRNA vaccination provides more immunity to severe Covid-19 than natural infection. Keystone / Laurent Gillieron

Swiss immunology experts estimate mRNA vaccination could provide more than two times the length of protection against severe Covid-19 infection than natural infection.

In a policyExternal link brief published on Friday, the Swiss National Covid Science Task Force writes that after mRNA vaccination, individuals below 65 years of age likely maintain more than 50% protection against mild infection for 16 months or longer and more than 80% protection against severe infection for more than three years.

This is 3-6 months and 10-12 months more than after natural infection. For the same age group, the scientists estimate that there is 16 months protection from severe disease after natural infection.

In people over 70 years old, the protection is expected to be shorter. The scientists estimate that protection against severe infection may last for up to 2 years.

The estimates use data modelling based on recent scientific evidence on B and T cell responses after vaccination or infection.

The authors caution that these are preliminary estimates that rely on several assumptions and extrapolations of existing data. A true immunologic correlation of protection from SARS-CoV-2 infection has not been identified. The findings may also not be accurate in the face of highly transmissible variants. “Protection against such variants is predicted to be significantly lower and shorter lived,” write the authors.

The protection duration can help inform when booster shots should be given and the length of validity for Covid-19 certificates. Based on the findings, a booster shot for lower risk individuals may not be necessary within two years. For people over 70 years old, a booster may offer benefits if administered within one year.

The scientists also recommend that the sequencing of viral variants is accompanied by monitoring of risk groups for premature reductions in immunity to severe infection.