How Effective Are the Vaccines Against Omicron Variant BA.5?

The Omicron variant BA.5 is now predominant in the U.S. and accounts for more than 80% of total COVID-19 cases. Even though the new strain is thought to be fourfold more resistant to vaccine-induced antibodies, getting a jab prevents developing severe symptoms and hospitalization.

The Centers for Disease Control and Prevention (CDC) data shows that from July 17 to July 23, Omicron subvariant BA.5 represented 81.9% of the total confirmed COVID-19 cases in the U.S.

The World Health Organization’s (WHO) expert Dr. Maria Van Kerkhove described BA.4 and BA.5 as "the most transmissible variants that we have seen yet."

Dr. Gregory Poland, head of Mayo Clinic's Vaccine Research Group, called Omicron variant BA.5 "hypercontagious," but noted that currently, there is no evidence that it leads to a higher death rate.

Vaccines prevent hospitalization

The new study on Omicron variants BA.4, & BA.5, published in the peer-reviewed science journal Nature, says that the strains are 4.2-fold more resistant to antibodies stimulated by RNA vaccines than previous variants of Omicron. This is why the newest variants are "more likely to lead to vaccine breakthrough infections," the authors conclude.

Epidemiologist Allison Krug, MPH, says that despite mutations in the new strains, vaccination works very well against severe diseases because "we don’t need a precise match to win the battle."

"The immune system works overtime between doses of vaccine and exposure to the virus to prepare a wide variety of different antibodies – each shaped slightly differently – in anticipation of a mutation in spike. This is what the body does after every exposure. Antibodies that fit well take time to produce en masse, so this is why you get sick, but don’t go to the hospital," she says.

Meanwhile, the BA.5 variant poses greater health risks for the unvaccinated, who account for 23% of the U.S. population. According to Mayo Clinic’s Dr. Poland, they are fivefold more likely to get infected with the BA.5 variant than those vaccinated and boosted. The unvaccinated are also about 7½ more likely to be hospitalized and 14-15 times more likely to die if infected.

The U.S. Food and Drugs Administration has already recommended COVID-19 vaccine manufacturers to include Omicron BA.4/5 components for their booster doses.

Half of the infected don't show symptoms

Krug, the epidemiologist, says that the only way to prevent the infection is to gain "mucosal immunity" defenders lining the mucous membranes of the nose, upper airways, and throat.

This type of immunity is acquired by being previously infected with COVID-19. The more recent the infection, the closer the match of the antibodies to the next variant to come around. The recently infected person also has a higher level of antibodies.

According to a new preprint on the new Omicron variants from researchers in Qatar, "People with previous SARS-CoV-2 infection from any variant had about 15% protection against BA.4/BA.5 infection. People who were infected with an Omicron variant had about 76% protection against BA.4/BA.5."

And those who have not been infected will "inevitably" catch COVID-19 but will not necessarily develop symptoms, Krug says.

President Joe Biden has also not escaped the BA.5 variant and tested positive for COVID-19 last week. Biden, who is 79 years old and double-boosted, experienced only mild symptoms, such as runny nose, fatigue, and dry cough. The president was treated with the new COVID-19 drug Paxlovid.

Krug says the symptoms of BA.5 infections are more likely to include fever, cough, sore throat, muscle aches, or headache. Meanwhile, the loss of taste or smell, the symptom that was common in people with Alpha and Delta variants, is less likely.


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