Risk of re-infection with Omicron

At the present time, a lot of people have been infected with Omicron. Now, BA.2, a contagious sub-variant of Omicron, is rapidly spreading around the world.

Currently BA.2 prevails over the other versions of the Omicron variant (including BA.1, BA.1.1 and B.1.1.529).

As pandemic restrictions have been lifted in some countries, the number of BA.2 infections has increased sharply. That makes many people worry whether they will be re-infected with Omicron or not?

Illustration: Dhakatribune

Omicron reinfection can occur but is not common

Scientists in Denmark, where BA.2 is widespread, discovered that reinfection with BA.2 despite having had BA.1 is possible, but quite rare.

Looking at data from more than 1.8 million patients over a 3-month period from November 2021 to February 2022, they found only 47 cases of BA.2 infection after BA.1. Most of the cases are in young, unvaccinated people. In the UK, out of more than 500,000 samples taken during the same time period, there were only 43 cases of reinfection.

However, the surveys were conducted over a very short period of time. It’s not clear how long Omicron immunity can last and if it varies between people.

Several laboratory analyzes have shown that BA.1 infection provides cross-protection against BA.2.

The New England Journal of Medicine in March published a review of blood samples from 24 vaccinated people who had never been infected with Covid-19; 7 people recently vaccinated and infected (so probably had BA.1); 1 person has not been vaccinated and has been infected. Statistics show:

– The subjects most susceptible to BA.2 infection are unvaccinated people who are not infected with BA.1.

– The booster shots seem to be quite useful to increase the levels of antibodies against both BA.1 and BA.2 in people who have never been infected.

– The group that is best protected against BA.2 are those who have been vaccinated, boosted, and been infected.

– The vaccinated group, who had been infected with Covid-19 (presumably BA.1) had three times higher levels of neutralizing antibodies against BA.2 than the others.

That suggests that there is a natural cross-innate immunity to BA.2 from BA.1.

The booster shot will probably fight BA.2 as well as other versions of Omicron. The remaining question is how long the effects of the 3rd shot last.

Research in Qatar from the end of December 2021 to the end of February 2022 noted:

– Having been infected with Covid-19 reduces the risk of BA.2 infection by 46%

– Complete 3 doses of vaccine to prevent infection 52%

– “Hybrid” immunity (2 doses of vaccine and previous infection) reduces the risk of BA.2 infection by 55%

– “Hybrid” immunity plus recent booster shot reduces the risk of infection by 77%.

An Yen (According to Insider)