Variant BA.5 spreads quickly, can evade immunity from vaccines and natural infection, but causes less severe symptoms.
After several consecutive weeks of decline, the number of Covid-19 cases in many regions increased again, mainly due to the spread of Omicron’s subtype BA.5. The World Health Organization (WHO) has classified it as a “disturbing strain”, recommending that countries raise their vigilance.
On June 27, Professor Phan Trong Lan, Director of the Department of Preventive Medicine, Ministry of Health said that Vietnam also recorded BA.5 infections. Mr. Lan said that the invasion of new strains was warned in advance, is inevitable due to the opening of economic exchanges and the realization of the new normal.
BA.5 first appeared in South Africa in January, causing a relatively small wave in May and is waning. However, in Portugal, mutations are reported in 80% of new infections. BA.5 also accounts for more than 21% of current cases in the US, according to estimates by the Centers for Disease Control and Prevention (CDC).
BA.5 is also available in Portugal, Germany, UK, Denmark, France, Austria, Belgium, Hong Kong, Australia, Canada, Israel, Norway, Pakistan, Spain and Switzerland.
The ability to evade immunity
BA.5 shares the same genetic origin with earlier Omicron strains. It possesses separate mutations, L452R and F486V in the spike protein, which helps the virus attach to the host effectively and evade the body’s immune response.
Paul Bieniasz, a professor at Rockefeller University, said BA.5 can cross the antibody barrier caused by vaccination or previous natural infection. To confirm this, scientists at Columbia University tested antibodies from people previously infected with Omicron with subtypes. They found they were effective against BA.1 and BA.2, but decreased their effectiveness several times before BA.5.
Scientists consider this to be part of a natural tendency in the evolution of viruses.
“Future strains will have many mutations that will allow them to evade the antibodies that people make after vaccination or disease,” said Professor Bieniasz.
Easy to spread but not necessarily cause severe symptoms
Experts say that BA.5 has a faster spread rate than the previous Omicron version. According to estimates by the US CDC, in the first week of May, two sub-variants appeared simultaneously, BA.5 and BA.4 accounted for about 1% of infections nationwide. By June 11, the infection rate had increased to 22%.
When compared across the same geographic region, Professor Trevor Bedford, Fred Hutch University’s Department of Public Health Sciences found that BA.2 had a growth rate of 0.05 per day, while BA.5 and BA.4 has rates of 0.09 and 0.14 per day, respectively.
“This suggests that BA.5 and BA.4 are more contagious (possibly due to the F486V mutation and other mutations in the genome). We speculate that BA.4 and BA.5 may increase more rapidly. BA.2 and BA.2.12.1”, said Professor Bedford.
However, BA.5 does not appear to cause dangerous symptoms. According to some experts, this is because the new strain spreads more effectively in the upper respiratory tract (nose and throat) than the lungs, causing fewer deaths than in the previous phase of the pandemic.
Experts have not yet concluded on the characteristic symptoms of BA.5. However, they believe that the symptoms of the patient will be similar to the previous strains of Covid-19, including stuffy nose, body aches, sore throat, sneezing, headache, cough, fatigue.
Impact on vaccines and treatments
Typically, a vaccine’s preventive effectiveness declines over time, meaning “nobody is completely protected against BA.5,” says virologist Alex Sigal, head of the Sigal Laboratory, Institute of Health Research. Africa, comments. People can still contract the virus despite being vaccinated, which will happen more often than in past strains.
New subtypes may also reduce the effectiveness of monoclonal antibody therapy. This therapy uses proteins from laboratory-generated Covid-19 antibodies. These proteins are usually based on the previous strain of nCoV.
“Most of those antibodies are outdated. Currently, only the drug from Eli Lilly has been developed specifically against Omicron. Still, other treatments such as the antiviral drug Paxlovid are still helping to reduce the risk. severe symptoms,” said Professor Bieniasz.
In addition, Assoc. Prof. Dr. Tran Dac Phu, former Director of the Department of Preventive Medicine (Ministry of Health), Senior Advisor of the Center for Emergency Response to Public Health Events, said that countries have experienced experience in epidemic prevention and control, the appearance of BA.5 is not a cause for concern.
“We need to properly assess the risk, to what extent it can be met. Avoid the phenomenon of underestimation, affecting the anti-epidemic results or vice versa, overestimating it, leading to a ban that affects the economy. , life,” said Mr. Phu, adding that people should go for booster shots as recommended.
Thuc Linh (Follow DW, Time, Medical News Today)