The BA.2 subvariant of Omicron is more contagious and can reinfect people, but it is not as severe, according to studies.

• This week, Danish scientists confirmed that the new subvariant can reinfect people who have previously had omicron, although it is not very common.
• The new variant of omicron, BA.2, is more contagious than the original BA.1, which is still prevalent globally.
• Despite the initial concern, the second wave of omicron infections is not being driven globally. In fact, Covid cases have decreased by 21% over the past week.

The BA.2 subvariant of omicron, which is more contagious, is gaining popularity worldwide and may soon become the dominant form of Covid-19.

The BA.2 variant of Covid-19 is now the top variant in 18 countries and accounts for 35% of all new cases that have been genetically sequenced worldwide, up from 10 countries and 21% of cases the week before, according to new data from the World Health Organization. In the U.S, BA.2 currently makes up 3.8% of genetically sequenced Covid cases, according to the Centers for Disease Control and Prevention.

The public is concerned about two things during the pandemic: whether BA.2 will cause a surge of omicron cases and if it will lead to more severe infections resulting in hospitalization. Scientists believe the answers to these questions are likely negative.

Scientists in Denmark have confirmed that a new subvariant of omicron can reinfect people who have previously had the virus, although it is not very common. Additionally, they have stated that this subvariant is more contagious than the original version of omicron, BA.1, which is still widely circulating globally.

Despite the belief that it might be driving a second wave of omicron infections, globally, Covid cases have decreased by 21% over the past week, with the exception of the Western Pacific region. Additionally, deaths have also decreased by 8% over the same period, according to data from the WHO.

The WHO's Covid-19 technical lead, Maria Van Kerkhove, stated that the global health agency is closely monitoring countries with BA.2 detection, but there has been no surge in cases caused by this subvariant yet.

Van Kerkhove stated during a livestreamed question-and-answer session on the WHO's social media platforms that although there is a decline in cases in countries, there is no increase with BA.2.

Here’s what’s known about the subvariant so far.

More transmissible

BA.2, a subvariant of the coronavirus, is 30% more transmissible than BA.1, according to Danish researchers. Denmark was among the first countries to experience the dominance of BA.2, and public health authorities worldwide have closely monitored the situation there to gain insight into its potential impact on the future course of the pandemic.

A study by a team of scientists from Danish public health authorities and the University of Copenhagen concluded that Omicron BA.2 is significantly more transmissible than BA.1, although the study has not yet been peer-reviewed.

BA.2 has a substantial advantage over BA.1 in England, according to the U.K. Health Security Agency, which found that BA.2 has an increased growth rate that can be seen in all regions in England, as stated by Dr. Susan Hopkins, the agency's chief medical advisor.

Mehul Suthar, a virologist at Emory University, stated that if BA.2 is indeed slightly more transmissible than BA.1, it is likely to replace BA.1 wherever it was reported.

According to Suthar, the emergence of BA.2 does not guarantee a surge in infections. The potential for BA.2 to cause another wave depends on its ability to reinfect individuals who have already recovered from omicron.

Reinfection possible, but appears rare

On Tuesday, Danish scientists confirmed that the BA.2 subvariant can reinfect people who previously had the BA.1 omicron variant, although the risk of catching the virus again is low.

A study by the Statens Serum Institute in Copenhagen found that 47 people caught BA.2 less than two months after infection with BA.1. The majority of those reinfected with BA.2 after BA.1 were under 20 years old and unvaccinated.

Despite the high number of positive SARS-CoV-2 tests during the study period, the reinfection rate seems low, but the authors emphasize the importance of continuous evaluation of vaccine-induced and/or natural immunity duration.

The study found that people reinfected with a BA.2 infection had mild symptoms and none of them were hospitalized or died. Additionally, the study discovered that people reinfected had a reduced viral load, indicating some crossover immunity from their first infection.

A separate study by the U.K. Health Security Agency found 69 cases of people reinfected with BA.2 within 90 days of their first infection with Covid. However, no instances of people reinfected by BA.2 after first catching BA.1 were found among the 51 cases where enough information was available. The timing of the first infections and sequencing indicated their original Covid cases were the delta variant.

Neither of the studies has undergone peer review, which is the standard in academic publishing. Due to the urgency of the pandemic, scientists have been rapidly publishing their research.

According to the WHO, early studies of reinfection cases in the general population indicate that one infection with BA.1 provides strong protection against reinfection with BA.2.

Andrew Pekosz, a virologist at John Hopkins University, stated that BA.2 may have encountered a population with a lot of preexisting immunity that targets it, which could be the reason why it's not growing as quickly as BA.1 omicron.

Doesn’t appear more severe

A study in South Africa, yet to be peer-reviewed, revealed that BA.2 causes illness similar to BA.1 omicron, but generally does not make people as sick as the delta variant. In other words, BA.2 does not cause more severe disease.

The National Institute for Communicable Diseases in South Africa discovered that 3.6% of BA.2 patients were hospitalized compared to 3.4% of BA.1 patients. Additionally, 30% of BA.2 patients who were hospitalized were severely ill, compared to 33% of BA.1 patients. The study was conducted on over 95,000 individuals who were tested for Covid from December through January.

The BA.2 variant, in terms of clinical severity, is behaving similarly to BA.1, with a reduced severity compared to previous variants, including the delta, according to Cheryl Cohen, one of the study's authors, who spoke at a news conference streamed on YouTube earlier this month.

Officials from the World Health Organization have consistently stated that there is no evidence to suggest that BA.2 is more severe. Cohen, however, pointed out that while the data from South Africa is reassuring, it is crucial not to make assumptions about other countries based solely on these results.

Cohen advised caution when extrapolating to other countries where most immunity comes from vaccination, as opposed to South Africa where most immunity is from natural infection, which could potentially provide a more robust protection against BA.1 and BA.2 for those who have had natural infection.

A study revealed that mutations on the BA.2 spike protein led to more severe lung infection in hamsters compared to BA.1. The virus utilizes the spike to invade cells, and vaccines target this protein to prevent infection. The Japanese research team suggested that the WHO classify BA.2 as a variant of concern due to its potential severity.

The virologist at Emory, Suthar, advised caution when interpreting the results of the Japanese study because it does not utilize the actual BA.2 strain. He stated that mutations in a single component of the virus, such as the spike, do not necessarily indicate that the virus is more severe.

The study on the effects of BA.2 on COVID-19 severity has not been peer-reviewed, and one of the scientists involved in the study stated that the results may not hold up in the real world due to the use of an engineered version of BA.2. The team replaced BA.2's spike protein with that of the original Wuhan virus in their study, according to Takashi Irie, one of the authors. Irie acknowledged in an email to CNBC that more reports are showing no increase in severity in BA.2 compared with BA.1.

Although Irie wrote that the study's finding that BA.2 is more pathogenic than BA.1 may not be accurate, he stated that the study's results suggest that mutations on the BA.2 spike can cause more severe infections.

A research conducted in Japan discovered that the BA.2 virus, which was isolated from a traveler who arrived in Japan from India, had a similar level of severity to BA.1 in mice and hamsters. However, the study has not undergone peer-review.

The WHO's Covid variant advisory group concluded that BA.2 should remain classified as omicron rather than being designated a separate variant of concern after examining the South African and Japanese studies, among others. This implies that the WHO does not currently consider BA.2 to be a greater threat to global health than omicron as a whole.

Vaccines

BA.2, a variant of the omicron virus, is better at evading vaccine protections than BA.1, according to a study published last month.

Vaccinated individuals who experience breakthrough infections are less likely to spread the virus to others, as they have a lower viral load, according to a study. This suggests that vaccines still play a role in reducing the spread of the virus.

A study published in early February revealed that BA.2 evades the antibodies from two doses of Pfizer's vaccine slightly more than BA.1. Neutralizing antibody levels were about 1.4 times lower against BA.2.

According to Dan Barouch, the lead author of the study and principal investigator at Harvard's Center for Virology and Vaccine Research, BA.2 evades antibodies from Pfizer vaccines in a similar manner to BA.1, with only a slight difference.

According to Barouch, individuals who have been vaccinated with BA.1 omicron also developed strong antibodies against BA.2, indicating that they likely have a significant level of immunity to the latter.

The effectiveness of two vaccine doses against symptomatic disease decreased to similar levels against BA.1 and BA.2, according to a report published by the U.K. Health Security Agency on Feb. 24. Booster shots increased protection to 69% against BA.1 and 74% against BA.2 two weeks after the third dose, the study found.

The Danish Statens Serum Institute analyzed a randomly selected sample of 263 reinfection cases.