Africa Defense Forum
ADF is a professional military magazine published quarterly by U.S. Africa Command to provide an international forum for African security professionals. ADF covers topics such as counter terrorism strategies, security and defense operations, transnational crime, and all other issues affecting peace, stability, and good governance on the African continent.

BA.4, BA.5 Strains Beat Immunity Better Than Predecessors


After giving rise to a new wave of infections in South Africa, the BA.4 and BA.5 strains of COVID-19’s omicron variant are rapidly sweeping through other countries because of changes that make the strains more contagious and more able to overcome existing immunity.

As with previous variations of COVID-19, BA.4 and BA.5 have evolved changes to their spike proteins, which are the “keys” the virus uses to unlock the body’s cells and use them to replicate.

Studies in Africa, Europe and North America show that the new strains — first reported in South Africa in January and February — can slip past protections provided by mRNA treatments and boosters and by natural immunity created by previous infections.

BA.5 is four times more resistant to protective medications than the omicron BA.2 strain that spawned it, according to studies.

During a recent news briefing, Africa Centres for Disease Control and Prevention Acting Director Dr. Ahmed Ogwell noted that BA.5 makes up about 21% of all new COVID-19 cases on the continent. BA.4 accounts for 19% of new cases.

Ogwell said test positivity rates remain around 11%. North Africa accounts for 67% of new cases.

“As we see subvariants emerge, it is not surprising that they are capable of evading immunity,” Dr. Clarence Buddy Creech, director of the Vanderbilt Vaccine Research Program at Vanderbilt University in Tennessee, told Medical News Today. “Variants that are easily neutralized by our immune system will have a difficult time becoming the dominant strain now that the vast majority of individuals have been vaccinated or infected with COVID-19.”

The older a person’s immunity, the greater the risk of contracting BA.4 or BA.5, according to studies. Preliminary research from Qatar shows that natural immunity acquired within the past 14 months remains 97% effective against severe disease from breakthrough infections by BA.5 and other recent strains.

Researchers still are determining exactly how contagious BA.4 and BA.5 are. One study in Australia suggests that a single person with BA.5 can infect more than 18 others — an infection rate similar to measles. By comparison, the delta variant had an infection rate of seven.

Unlike the delta wave, which was among the deadliest since the pandemic began in early 2020, BA.4, BA.5 and other strains derived from the omicron variant have produced far fewer deaths and hospitalizations for those with existing immunity.

According to South Africa’s National Institute for Communicable Disease, the BA.4/BA.5 death count was about one third the size of the original omicron wave in January. Hospitalization numbers were similarly low.

“Right now, we don’t have any evidence that it leads to a higher death rate, so that’s good,” Dr. Gregory Poland of the Mayo Clinic in Minnesota said during a recent video briefing.

People without immunity are five times more likely to get infected by BA.4 or BA. 5 than those with immunity, Poland added.

“We hope that there is enough underlying immunity that we will not see severe illness, and some studies indicate this,” Dr. Amira Roess, professor of global health and epidemiology at George Mason University in Virginia told Medical New Today. “Other studies show that severe illness is mainly observed among those who have significant underlying conditions or are of advanced age.”

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