The question that remains on people’s minds is how effective and long lasting the immunity is from either having had the COVID-19 infection or the vaccine. Now we are starting to get some answers. According to a population-wide study in Australia using data from the SARS-CoV-2 national infection reporting system, the re-infection rate has been low.

Researchers compared the odds of SARS-CoV-2 re-infections of COVID-19 survivors of the first wave (February- April 30, 2020) versus the odds of first infections in the remainder general population (by tracking PCR confirmed infections of both groups) during the second wave (September 1st-November 30, 2020). Out of the almost 15,000 COVID-19 survivors of the first wave and 253,000 infections in the 8.9 million individuals of the remaining general population, only 40 tentative re-infections were recorded.

This shows a relatively low re-infection rate of SARS-CoV-2 in Australia. Assuming that convalescents were exposed to COVID-19 at the same rate as people in the general population during the second wave, reduction in risk for re-infection was >90% which lasted for at least 7 months. Protection against SARS-CoV-2 after natural infection is comparable with the highest estimates on vaccine efficacies. Based on this data, there appears to be considerable protective immunity for at least 7 months after COVID-19 infection and no urgent need for booster vaccinations in COVID-19 convalescents. More well-designed research is needed for improving evidence-based public health decisions and vaccination strategies.

Reference: Pilz S et al. SARS-CoV-2 re-infection risk in Australia. Eur J Clin Invest 2021 April; 51:e13520.