Omicron BA.5: What we know about this COVID-19 strain

Updated Oct. 19, 2022

The omicron subvariant of COVID-19, BA.5, has become one of the dominant strains of the virus in the U.S. It's the most easily spread strain to date and is able to evade immunity from COVID infection and vaccination.

If you've been exposed to someone with the virus or have COVID-19 symptoms and are waiting for a test or your results, stay home and isolate from others.

Learn more about when you should get tested

You can also reach out to our experts using UC Davis Health’s convenient Telehealth Express Care for urgent needs or extended-hours video visits. Express care services are open Monday – Friday, 8 a.m. to 8 p.m. and Saturday – Sunday 9 a.m. to 6 p.m.

Learn more from our experts about omicron BA.5 and how you can protect yourself

All of the variants, including omicron BA.5, cause similar COVID-19 symptoms:

  • runny nose
  • cough
  • sore throat
  • fever
  • headaches
  • muscle pain
  • fatigue

Even people who have partial immunity from a previous infection or vaccination can still have a breakthrough infection. Breakthrough infections are in people who have been vaccinated or previously had COVID. However, the majority of breakthrough infections are not causing severe illness, as compared to early in the pandemic when no one had immunity.

New research finds that with each repeat COVID infection – even asymptomatic infection – your risk for complications increases. These include:

  • stroke
  • heart attack
  • diabetes
  • digestive and kidney disorders
  • long-term cognitive impairment, including dementia

Each reinfection also carries with it the risk of long COVID or ongoing COVID symptoms that can last for weeks or months after infection.

See which COVID-19 symptoms you should watch for

At-home COVID test instructions, accuracy, and where to find one

Learn more about omicron BA.5 and how you can protect yourself

Influenza (flu) and COVID-19 are both contagious respiratory illnesses, and they have similar symptoms. It may be hard to tell the illnesses apart based on symptoms alone, but there are three key differences, according to the CDC:

  • Those infected with COVID-19 sometimes experience change in or loss of taste and smell, which is less common with the flu.
  • Flu usually begins with a cough, whereas COVID-19 most often starts with a fever.
  • People infected with flu typically develop symptoms 1-4 days after infection. Those with COVID-19 typically develop symptoms 3-4 days after being infected. However, people infected with COVID-19 can show symptoms as early as 2 days or as late as 14 days after infection.

You can get your flu shot and COVID-19 bivalent booster from UC Davis Health.

Learn more about the flu and how to get your flu shot from UC Davis Health

Learn more about about COVID-19 symptoms

Yes, COVID-19 vaccines continue to provide good protection against the BA.5 variant. Vaccines are especially good in preventing severe disease that may cause hospitalization.

Since the bivalent boosters, known as the "updated boosters" are so new, there is no effectiveness data available yet. However previous, studies show that bivalent vaccines result in a stronger immune response against current variants such as BA.5 and help protect against the original strain. The bivalent vaccines also broaden the immune response, which is expected to improve protection against future variants and extend the strength of protection.

The bivalent booster vaccine is approved by the U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC). It’s an mRNA vaccine that targets the original SARS-CoV-2 virus and another component found in both the omicron BA.4 and BA.5 strains. Moderna and Pfizer both have a single-dose bivalent vaccine. Moderna’s bivalent booster is available to ages 18 and older, while Pfizer’s bivalent booster is for ages 12 and older.

UC Davis Health is offering bivalent boosters for anyone at any of our COVID-19 vaccine clinic locations. You can schedule your bivalent vaccine through MyUCDavisHealth (non-patients without a login will have to create an account) or by calling 916-703-5555. (In MyUCDavisHealth, click on Visits > Schedule Appointment > COVID Vaccination. You will then be prompted to answer which vaccines you have received already.)

Read more about bivalent boosters from the FDA

View the California Department of Public Health's statement on bivalent vaccines

Yes. According to the CDC COVID tracker, BA.5 is the predominant strain of COVID-19. It is more easily spread than other strains because it evades immunity from past COVID-19 infection and vaccination. That means even if you were infected with delta or omicron BA.1, you can still get BA.5. Your previous immunity does not protect you from the latest strain.

Learn more about omicron BA.5 and how you can protect yourself

Omicron BA.5 is more likely to cause less severe illness compared to other variants. The majority of breakthrough infections (people who have been vaccinated or previously had COVID) are not resulting in severe illness. Given how infectious BA.5 is, it’s important for everyone to take all precautions, including getting vaccinated and wearing a well-fitted face mask (N95 or KN95, if possible).

New research finds that with each repeat COVID infection – even asymptomatic infection – your risk for complications increases. This includes an increased risk for:

  • stroke
  • heart attack
  • diabetes
  • digestive and kidney disorders
  • long-term cognitive impairment, including dementia

Each reinfection also carries with it the risk of long COVID or ongoing COVID symptoms that can last for weeks or months after infection.

Read more: 9 things we've learned about long COVID so far

To protect against omicron BA.5, health experts recommend the following:

Learn more about omicron BA.5 and how you can protect yourself

At-home COVID test instructions, accuracy, and where to find one

Most people who test positive with any variant of COVID-19 typically experience some symptoms for a couple weeks. People who have long COVID-19 symptoms can experience health problems for four or more weeks after first being infected, according to the CDC.

At-home COVID tests, also known as rapid antigen tests, are useful because they provide quick results. Tests can be purchased without a prescription and are available at pharmacies and stores. At-home test brands include BinaxNOW and iHealth. You can also sign up to get four free COVID test kits that are mailed to you from the federal government.

If you've been exposed to someone with COVID-19 or are having symptoms, at-home tests can give you a good sense of whether or not you have an infection. These tests are pretty reliable, but they're not perfect.

  • If you have COVID-19 symptoms and test negative, you still might have COVID-19 and should stay away from others.
  • If you have COVID-19 symptoms and test positive, you can trust that positive result. You can always request a diagnostic or PCR test from your physician to confirm that result. If you test positive, isolate for at least five days, as recommended by the CDC.

Watch this video for tips on using at-home tests

Learn what to do if you test positive for COVID-19

At-home COVID test instructions, accuracy, and where to find one

Several studies, including one from UC Davis, indicate how effective masks can be in protecting yourself and others. It’s important to remember that you may be asymptomatic and not know you are infected but still able to spread COVID-19. Wearing a mask in these situations helps protect vulnerable people you could unknowingly infect.

Mask guidance continues to change, depending on rates of spread within communities, as well as the levels of vaccination and immunity people have from both vaccination and infection. Even if masking is not required, consider wearing a mask in public indoor spaces if you or people you live with are at high risk for severe disease.

Consider upgrading your face masks to N95s or KN95s if you want more protection. Cloth masks reduce the risk of infection by about 50%. This is compared to surgical masks that reduce the rate of infection by about 60-70%, and greater than 80% for N95s.

Learn more about which masks are best to protect against omicron BA.5

Yes. It’s important to know if you're infected with COVID-19 for three reasons:

  1. If your illness gets worse, you’ll want to know so you can take advantage of COVID-19 treatments.
  2. You need to know whether to isolate so you can reduce your chances of infecting others, especially those who are more vulnerable to severe COVID-19.
  3. You will want to notify anyone you were recently in contact with so they can monitor their symptoms and get tested if needed.

Most likely. Unfortunately, omicron is so easily spread that even those who are fully vaccinated and boosted may get the illness. If you know you had contact with an infected person, particularly in a higher-risk situation (such as an indoor space for a longer period with others who weren’t masked), testing is advised. You should also quarantine, watch for COVID-19 symptoms, stay away from others in your home, and wear a mask. If you test positive, then you should isolate.

However, if you were in a situation where people were outside, masked and distanced, the risk of infection is much lower. Instead of testing right away, you could monitor for COVID-19 symptoms and get tested if any develop.

Learn more about the difference between quarantine and isolation

Although it can vary, people are generally contagious between 1-3 days before omicron symptoms show.

The more people who are infected, the more likely we are to see new variants. The message from health experts remains that everyone should be vaccinated against COVID-19. Every time COVID-19 infects someone, there’s a chance for more mutations, which can allow the virus to keep spreading. Stay vigilant and get vaccinated if you haven’t already.

Learn how to schedule your COVID-19 vaccine at UC Davis Health