COVID-19 no longer provides long-lasting and durable immunity

New research shows that natural immunity after COVID-19 infection has declined dramatically since Omicron became the dominant option.

At the peak of the COVID-19 pandemic, the only relief in seeing two lines on a rapid test confirming infection was that you would be protected from re-infection for some time.

A study published in Nature found that since Omicron became available in late 2021, there is effectively no natural immunity to COVID-19.

Before Omicron, infection meant 80 percent protection against re-infection for a year. After Omicron, this dropped to 5% protection after one year, underscoring that for people with weakened immune systems, vaccination is more important than ever.

The evolution of the Omicron variant marked a significant shift in the way COVID-19 spread – it became much more infectious than previous variants and was also able to better evade vaccines.

In addition, there is evidence to suggest that Omicron may evade natural defenses against previous COVID-19 infection and therefore be more likely to lead to re-infections.

Testing at the whole population level

Hiam Chemaitelly of Weill Cornell Medicine-Qatar, Cornell University, Qatar Foundation, Doha, and colleagues studied the strength and duration of natural immunity in a Qatari population before and after infection with Omicron virus.

In the group with infection before Omicron, natural immunity protected individuals after re-infection with COVID-19 virus by 81% three to six months after initial infection; after one year, protection was maintained at 80%.

Instead, in the group with post-Omicron infection, protection against re-infection dropped from 78% after three to six months to 60% after six to nine months, and dropped to 5% after one year.

To make sure vaccination status didn’t bias the results, the researchers analyzed infections before and after Omicron according to whether people were vaccinated or not, and the results were very similar.

An important finding, the researchers said, is that despite re-infection, previous infection still provides “robust and durable protection against the severe form of COVID-19, with no weakening of this protection.”

Shifting evolutionary pressures

The researchers hypothesize that the change in natural immunity after Omicron is due to different evolutionary pressures on the virus.

Before Omicron, many people had weak immunity – especially before vaccines began to spread – so the main challenge for the virus was to disseminate among as many people as possible, so the virus evolved alpha and delta variants that were much more transmissible.

However, by the time Omicron became available in late 2021, many people, particularly in high- and middle-income countries, had already been vaccinated or infected with COVID-19 and had natural immunity. Omicron has thus evolved as the variant best suited to bypass immunity.

The research team says their findings point to the importance of continuing to monitor the virus as it evolves, and that it is critical to continue to provide COVID-19 vaccines to people with weakened immune systems.

Vitality Medical & Research Center Ukraine,KyivLeave a request

Published: 18.02.2025

Updated: 16.02.2025

Medical author, Medical editor:

Stepan Yuk

Medical expert:

PhD. Olexandr Voznyak