COVID immunity following natural infection likely short-lived: Study

Matt Woodley

21/10/2021 4:55:13 PM

New research suggests reinfection can occur in as little as three months, strengthening the argument for vaccination.

Alex Dornburg and Katerina Zapfe.
Assistant Professor Alex Dornburg with UNC Charlotte doctoral student Katerina Zapfe. (Image: UNC Charlotte)

A recently published study out of the Yale School of Public Health and University of North Carolina has found strong protection following natural infection is short-lived.
According to the research, reinfection by SARS-CoV-2 under endemic conditions would likely occur between three months and 5.1 years after the ‘peak antibody response’, with a median of 16 months.
And in some cases, that time could be even further reduced, the paper’s lead author Professor Jeffrey Townsend said.
‘Reinfection can reasonably happen in three months or less,’ he said.
‘Therefore, those who have been naturally infected should get vaccinated. Previous infection alone can offer very little long-term protection against subsequent infections.’
The researchers say the study is the first to determine the likelihood of reinfection following natural infection and without vaccination.
To produce their findings, the team analysed known reinfection and immunological data from the close viral relatives of SARS-CoV-2 that cause common colds, along with immunological data from SARS-CoV-1 (SARS) and Middle East Respiratory Syndrome (MERS).
They then combined genetic data from these viruses with SARS-CoV-2 itself to build a viral ‘family tree’ to model how viral traits evolve over time and provide an estimate of how quickly COVID antibody levels decline post-infection, alongside other factors needed to understand reinfection risk.
This approach allowed the scientists to model the likely risk of reinfection once SARS-CoV-2 becomes endemic, despite not having access to long-term real-world COVID data.
‘We don’t want to wait for that. And we don’t have to,’ Professor Townsend told Nature.
‘Immunity is relatively short-lived … you should still get vaccinated even if you got infected.’
The research suggests that the average reinfection risk increases from approximately 5% four months after initial the infection, to 50% by 17 months.
‘This protection is less than half the duration revealed for the endemic coronaviruses circulating among humans,’ the authors found.
‘As the COVID-19 pandemic continues, reinfection is likely to become increasingly common.
‘Maintaining public health measures that curb transmission – including among individuals who were previously infected with SARS-CoV-2 – coupled with persistent efforts to accelerate vaccination worldwide is critical to the prevention of COVID-19 morbidity and mortality.’
Study co-author Assistant Professor Alex Dornburg from the University of North Carolina said many people tend to think about immunity as ‘being immune or not immune’, but he said the focus should be on the risk of reinfection over time.
‘As new variants arise, previous immune responses become less effective at combating the virus,’ Assistant Professor Dornburg said.
‘Those who were naturally infected early in the pandemic are increasingly likely to become reinfected in the near future.’
However, while the peer-reviewed study was able to estimate the likelihood of reinfection, it was not able to determine how sick people who have been previously infected are likely to get.
Associate Professor Alexander Edwards from the University of Reading in the UK, who had no involvement in the study, told Medical News Today severity of infection is the ‘most important point’.
‘If previous infection protects from serious disease developing, it becomes less important to the individual if they get infected a second time,’ he said.
‘However, for COVID-19, we still don’t know if previous infection will fully protect from severe disease and death for everyone.’
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