AmericaPeople who have received a booster dose and have Covid-19 in the past can still be reinfected with BA.5, but symptoms are less severe.
In 2020, cases of re-infection with nCoV are considered very rare. In 2021, a breakthrough infection in vaccinated people will occur, but the risk is low. By 2022, the condition will become so much more common, reinfections and breakthrough infections are considered the norm.
British scientists have found that the risk of reinfection during the Omicron outbreak was eight times higher than in last year’s Delta wave.
“I wouldn’t be surprised to see people get sick more than once a year,” Dr. Anthony Fauci, President Joe Biden’s chief medical adviser, said in an interview in June. Still, he was lost. Covid-19 will eventually become a seasonal flu-like pathogen.
The risk of reinfection is now even higher, as subtypes BA.4 and BA.5 have predominate. They are the main reason for the high number of new cases in the US and around the world.
Dr Rochelle Walensky, Director of the Centers for Disease Control and Prevention (CDC), said the two subtypes were more transmissible and more immune-evasive than the previous version of Omicron.
“People who have had Covid-19 before, even with BA.1 or BA.2 are still at risk of contracting BA.4 and BA.5,” she said.
Experts agree that Vaccinated people, even with booster doses, can still get the virus again.
“Unfortunately, reinfection is quite normal. This is just the nature of the virus,” said Akiko Iwasaki, a professor of immunobiology at Yale University.
Fauci said other strains of coronavirus that cause colds can also re-infect. However, re-infections can occur every two or three years, because the virus does not mutate much.
However, nCoV is a completely different case. The subtypes of Omicron grow very rapidly and are effective at evading immunity. Combined with that is the natural decline in antibodies over time in humans. “It’s not surprising to see more and more cases of reinfection,” said Dr. Iwasaki.
This is especially true of people who were infected with the BA.1 variant last winter. BA.4 and BA.5 have quite different characteristics from the first version of Omicron, so there is “no guarantee” that people who have been infected with Omicron in the past will be safe during the new outbreak.
Experts It is not possible to estimate the number of reinfections in a person. Given the high level of transmission in countries like the US, anyone has a second or third chance of being exposed to the virus and getting re-infected.
Dr. Julie McElrath, director of the division of vaccines and infectious diseases at Fred Hutchinson Cancer Center in Seattle, explains that a person’s likelihood of reinfection depends on the strength of the immune response and vaccination status. She said asymptomatic infections are also an effective defense against the virus. After each exposure to the pathogen, the immune response matures and is further reinforced.
“We should treat reinfection as part of the new normal. Hopefully with multiple infections, the antibody response will continuously improve,” she said.
The question scientists repeatedly asked during the two years of the pandemic was: How long will the immunity of Covid-19 last after infection? Fauci said the scientific community has not yet had specific studies to conclude this.
“According to experience from other infectious diseases, it can be several months. This is when you really have enough sustained immunity to not be re-infected again. For the most part, the time of protection will be a few days. months, but (antibodies) will wane,” he said.
In many cases, patients re-infected within a shorter period of time, about 4 weeks. The Qatar study, which has not been peer-reviewed, found that people infected with Omicron for 6 months had 80% effective immunity against subtypes BA.4 and BA.5. However, antibodies from previous episodes (such as Alpha or Delta) were much less effective, only 28%.
Most cases of reinfection have less severe symptoms, thanks to the level of immunity.
A study in Qatar of nearly a million people showed that immunity from a previous infection was able to protect about 97% from becoming severe from any mutation. In other words, reinfection does not lead to severe symptoms. In addition, immunity from vaccines is also effective in preventing serious illness and death.
However, there are still cases of people developing dangerous symptoms after reinfection, for example people who are exposed to a much higher amount of the virus than the first time, or have completely weakened immunity. Fauci said people who are elderly, have underlying medical conditions or are immunocompromised can still turn severe.
Thuc Linh (Follow NBC News)