Updated: Jan 24, 2022
It was welcoming news to hear that people previously infected with SARS-CoV-2 who later became fully vaccinated would be 'hyper-immune' and possibly more protected from future infections. Their hybrid immunity makes more potent and higher levels of neutralizing antibodies than those who only had COVID-19 or were vaccinated. However, even such 'hyper-immunity,' also referred to as 'super-immunity,' seems to be fading over time and will probably need extra support, like the booster shots, to protect against the newer variants like Omicron.
Scientists from Israel studied how the 'super-immunity' holds up over time by studying a large cohort of 5.7 million people divided into three groups:
People who have been infected with the virus and are still unvaccinated,
People who recovered from the infection and are fully vaccinated, and
People fully vaccinated who have not been infected.
This research showed that there were initially seven times lower chances of infection among people who received just a single dose of vaccine following the natural infection than people who received both doses without prior infection. Unfortunately, the infection rate rose over time in every group since vaccination or infection.
Although the study predated the emergence of the Omicron variant, recent reinfections and breakthrough infections are likely to be caused by Omicron, suggesting hybrid or boosted immunity could still be vital in preventing severe COVID-19 infections.