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.