How many times can a person get Covid-19 again?

More and more people are re-infected with Covid-19 after only 1-2 months of recovery. Experts emphasize that we can be infected with nCoV many times, and vaccination helps reduce the risk of getting worse.

In early January, the Guardian reported on a case in Mea Walton, 20 years old, a female medical school student in the UK, infected with Covid-19 a total of 4 times. In September 2020, Walton was found to have Covid-19 shortly before leaving for school. At that time, she worked part-time in a pub and always wore a mask.

At the 2nd and 3rd Covid-19 infection, the female student felt uncomfortable because she had a runny nose. But, on the fourth time, a few days after testing positive, her symptoms resembled the flu.

Another case is Alon Helfgott, a 12-year-old Israeli boy infected with 3 strains of nCoV Alpha, Delta and Omicron respectively. At the time of Omicron infection, Alon's health was not affected much, nor did he have many symptoms. When he was infected with the Alpha variant, the boy had a high fever.

The above cases make many people worry after recovering from the disease, how high the risk of re-infection with Covid-19 is and how many times each patient can be re-infected with nCoV.

Protective antibodies from innate immunity and vaccines degrade over time. Therefore, all F0 who have recovered from the disease are at risk of re-infection with Covid-19. (Photo: Freepik).

How common is Covid-19 recurrence?

According to the US Centers for Disease Control and Prevention (CDC), the recurrence of Covid-19 is quite rare, but the results of investigation in many studies show that this trend is gradually becoming more common.

Cnet cited information from the CDC showing that the Delta variant is more contagious and the rate of reinfection with this variant may also be higher than that of Alpha or other strains. The appearance of Omicron makes this condition even more common.

Analysis by the UK Health Security Agency (UKHSA) published in December 2021 found that one in 10 people is infected with the Omicron variant in the country.

The study also showed that antibodies from a previous Covid-19 infection were strongly weakened before the new strain. Because Omicron carries mutations that avoid immunity from two doses of vaccine or previous nCoV infection.

Another study in the UK from November 29 to December 11, 2021 concluded that F0 was only 19% resistant to Omicron. This figure in people who have received two doses of the Covid-19 vaccine is similar, about 20%.

In addition, the booster shot is thought to protect 55-80% of the risk of symptomatic Omicron infection.

Why does F0 get Covid-19 so many times?

In an article on The Conversation, Professor Paul Hunter, University of East Anglia, UK, an adviser to the World Health Organization (WHO), said that the answer may be that our immunity is often not enough to prevent infection. prevent nCoV infection.

That may be due to the appearance of a new strain like Omicron with many mutations, which makes it difficult for the immune system to distinguish. In other words, the virus has already overcome immunity from a previous infection.

The second possibility is that the immunity we get from a previous Covid-19 infection or vaccination has weakened. The solution to this is booster shots.

The risk of re-infection with Covid-19, severe illness on a second infection is reduced by vaccination.

When the virus invades, the B and T cells work to fight the infection. Antibodies produced by B cells act as the front line of defense against infection and prevent the cells from getting infected, thereby protecting us from the risk of re-infection. Meanwhile, T cells destroy infected cells.

After the threat of the virus passes, the T and B cells die and the amount of antibodies decreases. Over time, the loss of antibodies creates an opportunity for the virus to enter a second time, especially when it mutates as much as nCoV, bringing more adaptive advantages to the body.

Viruses are constantly evolving and forming new mutations, new strains. If many populations remain unvaccinated or do not have immunity, experts fear there could be a strain that renders the vaccine ineffective.

In addition, nCoV almost always enters the body through the nose and throat. Meanwhile, mucosal immunity in these areas tends to be relatively short-lived compared with body-wide immunity.

This may also explain why protection against serious illness, which often originates in the lungs, lasts longer than protection against infection.

How long after recovering from F0 disease can I get Covid-19 again?

A UK study of 25,661 people from June to December 2020 found that F0 reduced the risk of re-infection with nCoV by 84% in the following 7 months. Less than 2% of volunteers tested positive for Covid-19 a second time.

However, the emergence of a new strain makes the protective ability of antibodies from the previous infection gradually shorten.

In October 2021, a study looked at the possibility of reinfection with different strains of nCoV and found that a person who has had Covid-19 can be reinfected within 3 months to 5 years if not vaccinated. The average duration was 16 months.

However, some F0 relapses earlier than this, even after 1-2 months.

Prof. Dr. William Schaffner, Vanderbilt University Medical Center, USA, said: 'Some people think that after recovering from Covid-19, you will be protected forever as if you had measles. But the two viruses that cause these two diseases are completely different. The ability to protect from nCoV will naturally lose over time."

This means that each person can re-infected with Covid-19 not only twice but many times.

An October 2021 study by the Yale School of Public Health found that unvaccinated people develop immunity against reinfection for about 3-6 months. However, this data was calculated before Omicron appeared.

And currently, experts emphasize that there is not enough data to know whether an F0 can re-infected Omicron many times or not.

However, UKHSA insists this risk is entirely possible. And vaccination is still the way to help protect us against the risk of re-infection.

The CDC cites a study that found that unvaccinated people were twice as likely to be reinfected as a group that received the Covid-19 vaccine.

Other research has also shown that unvaccinated people are 5 times more likely to be hospitalized if they get Covid-19 a second time.