Omicron Subvariant BA.5: What You Need To Know

The highly contagious subvariant of Omicron known as BA.5 has taken hold as the dominant subvariant in the United States, leading to a new surge in COVID-19 cases. For the week ending August 13, the Centers for Disease Control and Prevention (CDC) reported that BA.5 represented 88.8% of infections in the country, as case counts have risen to the highest point of the summer.

“The World Health Organization (WHO) has been tracking BA.5 since April, and it has caused spikes in cases around the world,” says Dr. Yoko Furuya, chief epidemiologist and medical director of Infection Prevention and Control for NewYork-Presbyterian Hospital. “Now it’s fueling a COVID-19 surge in the U.S.”

Dr. Furuya explains what people should know about the Omicron subvariant BA.5, including the most effective treatments, whether people can become reinfected, and how to continue to protect ourselves in the current phase of the pandemic.

How is BA.5 related to Omicron, and why is it so transmissible?
Dr. Furuya: Omicron is really a variant “family” of the virus that causes COVID-19, with multiple offshoots, or subvariants. These subvariants are closely related to each other, but they also have genetic mutations that make them behave a little differently from one another. BA.5 is one of these subvariants in the Omicron virus family, and it is now causing surges in COVID-19 infections in numerous countries. It seems to be the most transmissible variant of the coronavirus yet.

The fact that BA.5 has quickly become the dominant strain suggests that it is more transmissible than the prior strains, but exactly how much more transmissible is an issue that is currently being debated among scientists. The mutations in spike proteins are making it easier for the virus to penetrate human cells, escape antibodies, and cause infection.

Are patients getting sicker from BA.5? What are the symptoms?
It still remains to be seen whether BA.5 could cause more severe infection than other Omicron subvariants. Early data from Denmark and Portugal suggest that BA.5 could be associated with an increased risk of hospitalization compared to BA.2, but more data are needed to get a better handle on that issue.

Data from studies in the United Kingdom suggest that BA.5 seems to be associated with symptoms like fever, sore throat, abdominal pain, and muscle aches, in addition to cough. However, loss of smell and taste occur less often with BA.5 and the other Omicron subvariants than with earlier strains of the virus such as Delta. Hospitalizations have not increased to the same level as in prior waves of other variants like Delta, but it is unclear if that is due to the virus itself or the fact that most adults in many countries are now vaccinated and have access to antiviral treatments like Paxlovid.

What are effective treatments for the subvariant?
Paxlovid, the antiviral oral pill produced by Pfizer, appears to be effective against BA.5, as do other antivirals like molnupiravir and the intravenous antiviral drug remdesivir.

There has been a lot of attention to the phenomenon of “Paxlovid rebound,” where COVID symptoms can recur after they initially get better, and this has led some people to be reluctant to take Paxlovid. However, it’s important to remember that “rebound,” or the reappearance of COVID symptoms after they initially subside, is not dangerous, and if you are at higher risk of severe outcomes from COVID, then it’s still worth taking Paxlovid to reduce your risk of severe illness, hospitalization, and death.

More data on Paxlovid rebound are continuing to emerge, but the incidence is probably somewhere in the 3% to 4% range, although it varies from study to study from about 1% to 10%. However, a recent preprint study showed that this rebound effect is actually seen just as commonly with another antiviral oral pill, called molnupiravir, used to treat COVID, so the effect is not unique to (or worse with) Paxlovid. Perhaps even more importantly, another preprint study showed that this so-called “rebound” effect is commonly seen even in people who took no antiviral treatment for COVID-19.

This suggests that this “rebound” that has been blamed on Paxlovid is actually just part of the natural waxing and waning course of the virus, where symptoms can get better and then worse again before they subside. It is also not unusual for people to go from testing positive for COVID-19 to testing negative to testing positive again, regardless of whether they take Paxlovid or not.

So all of this to say that concern about “rebound” should not prevent higher-risk individuals from taking Paxlovid, since rebound is not dangerous and can occur even without taking Paxlovid or other antiviral treatments. Most importantly, the treatment continues to be effective at preventing severe disease and hospitalization. More information on who is eligible for antiviral treatment can be found on the Health and Human Services website on COVID-19 antivirals.

In terms of monoclonal antibody treatments, some appear to be more effective than others. The most effective are bebtelovimab, a monoclonal antibody used for treatment for mild infection in higher-risk people, as well as Evusheld (tixagevimab and cilgavimab), which is used as prophylaxis to protect against infection in moderately or severely immunocompromised people.

Are the vaccines protective against the Omicron subvariant BA.5?
All of the current FDA-authorized COVID-19 vaccines appear to protect against severe disease and hospitalization due to BA.5. However, several studies, including a recent clinical trial sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), have shown that the vaccines may be less effective at protecting against BA.5 than other vaccine strains, since BA.5 is better at evading the antibodies induced by the current vaccines than prior strains. This NIAID clinical trial also showed that antibody responses after a vaccine booster dose are initially high, but that these responses waned significantly after three months, so the protection may be more fleeting.

Finally, the clinical trial showed that antibody levels in people who got the Janssen (Johnson & Johnson) as both their primary vaccine and their booster had low antibody levels against Omicron as compared to those who received other vaccines, which supports the CDC’s general recommendation for mRNA vaccines such as Pfizer or Moderna over the Janssen (Johnson & Johnson) vaccine to protect against any COVID-19 strain, including BA.5.

If you are eligible for a booster or second booster, it’s recommended to get one.

What do we know about the adapted vaccines targeted to protect people from Omicron?
All of the currently available vaccines were developed to target the original COVID-19 virus, called the “ancestral” strain. The more time passes and the virus picks up more and more mutations, the less related current variants, like BA.5, are from the ancestral strain. In other words, BA.5 is less like a sibling of the original COVID-19 strain and more like a very distant cousin. So, not surprisingly, the original vaccines are less effective against BA.5 than they were against the older strains.

To address this problem, both Pfizer and Moderna have been developing what are called “bivalent” vaccines, in which the current vaccines have been expanded to target not just the ancestral COVID-19 strain but also Omicron. While these new vaccines were initially developed to target BA.1, preliminary data from both companies have shown that they are also more effective against BA.5 than are the current vaccines, and now both companies are again modifying their bivalent vaccines to target BA.4 and BA.5 specifically.

Based on this, the Biden administration just announced a plan to roll out a booster campaign in the fall with these bivalent vaccines targeting BA.5. Pfizer and Moderna have promised that the new vaccines will be ready sometime in September. While the boosters are expected to be recommended widely for more than just older and higher-risk adults, the details of exactly who will be eligible are not yet clear.

Are people who were infected with Omicron protected from BA.5?
Generally, people who were recently infected with BA.1 are protected from being reinfected with BA.5, although rare reinfections have been reported. Researchers from Weill Cornell Medicine-Qatar found that a prior Omicron infection was 79.7% effective at preventing a BA.4 and BA.5 reinfection.

However, we also know that the more time passes after a previous COVID-19 infection, the more your immunity wanes, so your risk of being reinfected, especially with a different strain, starts increasing after several months. Helix, a company which performs COVID-19 viral sequencing, has data showing that reinfections are more common with BA.5 than with BA.2, but most people who get reinfected are getting it, on average, nine months after their prior infection.

What should people keep in mind in terms of precautions and how to best protect themselves?
Knowing that COVID-19 isn’t going away anytime soon, we’re now all trying to figure out how best to live with the virus and how to adjust what we do based on future waves and variants that we are likely to see. First and foremost, the best way to protect yourself is to get vaccinated and to get a booster if you are eligible. Even with the big Omicron BA.1 wave, fully vaccinated people were much less likely to get infected than unvaccinated people, and they were also extremely unlikely to be hospitalized from COVID-19. This protection was even greater for people who had received the COVID-19 booster.

While the CDC and many states have relaxed masking requirements for areas with low community transmission of COVID-19, it’s important for people to be prepared to go back to masking and taking other precautions when the numbers go back up again. If numbers in your community go into the CDC high-risk level, it is recommended that you resume masking indoors. I would also consider avoiding large, crowded places as well as indoor spaces where masking is not feasible, such as indoor dining in restaurants and bars.

For some people, like those who are elderly or those with weakened immune systems, it may be prudent to keep taking precautions like masking indoors even if community transmission rates are low, but particularly when they start to go into the CDC medium-risk level. The same precautions might be considered if you live in the same household as someone who is elderly or has a weakened immune system, or people who encounter these types of individuals at work, such as healthcare workers.

Another consideration for everyone is to take extra precautions during the weeks leading up to a large social gathering, like a family get-together, or before a planned trip. Being vigilant about masking and avoiding potential exposures could prevent your plans from being interrupted or, even worse, lead to transmission to your friends and family.

Finally, even when community transmission is low, everyone should continue to take seriously any potential symptoms of COVID-19 (such as fever, cough, sore throat, head and body aches, etc.), self-isolate, and get yourself tested. Testing before large get-togethers may also be a good idea, especially if vulnerable people (elderly or immunocompromised) are attending.

Yoko Furuya, M.D., is a nationally recognized epidemiologist and specialist in infectious diseases, with 20 years of clinical experience. She is the medical director of Infection Prevention & Control and director of Antibiotic Stewardship for all campuses of NewYork-Presbyterian Hospital, including NewYork-Presbyterian/Columbia University Irving Medical Center and NewYork-Presbyterian/Weill Cornell Medical Center. She is also an associate professor of Medicine at Columbia University Vagelos College of Physicians and Surgeons. In 2018, Dr. Furuya was honored for her achievements in the field of healthcare epidemiology by being recognized as a Fellow of the Society for Healthcare Epidemiology of America (SHEA).