COVID-19 vaccine boosters and third doses

Updated Sept. 19, 2022

COVID-19 vaccine boosters and third doses are available for certain people. You can schedule your booster or third dose with UC Davis Health. Here's what you need to know from our UC Davis Health experts:

In late August/early September of 2022, the U.S. Food and Drug Administration (FDA) and the U.S. Centers for Disease Control and Prevention (CDC) approved an "updated booster" known as the bivalent vaccine for ages 12 and older. Pfizer's bivalent booster is approved for ages 12 and older, while Moderna's bivalent booster is approved for ages 18 and older. The CDC's recommendation is for everyone in this age range to get a bivalent booster, even if you've received one or more of the original (monovalent) boosters.

One thing to be aware of is that booster recommendations still vary among groups of people, depending on factors such as age, health status and the time since your last dose. For example, the CDC recommends that immunocompromised people ages 6 months and older get the original (monovalent) third vaccine dose. This group ages 5 and older should also receive a booster vaccine (fourth dose) from Pfizer or Moderna. Pfizer's bivalent vaccine is the only approved vaccine for ages 12-17.

If you're unsure when to get your booster and which booster you're eligible for, the CDC has a tool to help you decide. The tool prompts you to answer questions about your age range, when you've last received a vaccine or booster, and a few other pieces of information about your vaccine status. 

Find out when you're eligible for a COVID-19 booster 

Schedule your COVID-19 booster or third dose on MyUCDavisHealth

Learn more about bivalent boosters from the California Department of Public Health

Bivalent vaccines, which are being called the "updated boosters," contain two mRNA components of the COVID-19 virus. It includes the original SARS-CoV-2 strain and another strain that is common between the omicron BA.4 and BA.5 viruses.

Both Moderna and Pfizer-BioNTech have bivalent single-dose boosters that have been authorized by the FDA and CDC. Moderna's vaccine is available to people 18 years and older. Pfizer's bivalent booster is for people 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.)

Learn more about bivalent vaccines from the U.S. Food and Drug Administration (FDA)

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

The CDC recommends immunocompromised people ages 5 and older receive an additional primary dose of an mRNA vaccine from Pfizer or Moderna. (Pfizer remains the only vaccine approved for ages 5-17.) The additional dose must be given at least four weeks after the second dose of Pfizer or Moderna or at least four weeks after one dose of Johnson & Johnson. Some of the conditions and treatments that result in immunosuppression include, but are not limited to, the following:

  • Active cancer treatment for tumors or blood cancers
  • Organ transplant and is taking immunosuppressants
  • Received CAR-T therapy or a stem cell transplant within the last 2 years
  • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Advanced or untreated HIV infection
  • Taking immunosuppressants (such as high-dose corticosteroids)
  • Dialysis

Schedule your COVID-19 boosters or third dose through MyUCDavisHealth or on California's

View the CDC's breakdown of boosters for immunocompromised people

For patients with previous COVID-19 infections, the CDC has advised that more time between infection and vaccination may improve immune response. You may want to consider a 3-month interval before your first or second booster doses or discuss the timing of your booster with your physician. 

If you are eligible for a COVID-19 vaccine booster or third dose, UC Davis Health patients and non-patients can schedule an appointment at MyUCDavisHealth. You can also use California's vaccine scheduling portal.

Here are instructions to schedule your COVID-19 booster vaccination with one of our UC Davis Health locations:

  • Log into your MyUCDavisHealth account (on desktop or mobile)
  • Click "Visits" at the top
  • Click "Schedule an Appointment"
  • Scroll down and click COVID Vaccination (at the bottom on mobile or on the bottom right for desktop users)
  • Fill in the questionnaire, which will best guide you to the appropriate scheduling options.

Anyone who received a single dose Johnson & Johnson vaccine is eligible to received a booster shot or second dose of an mRNA vaccine (Pfizer or Moderna), according to the CDC’s criteria. To schedule a booster or second dose with UC Davis Health, please call 916-703-5555 Monday-Friday 8 a.m.-5 p.m.

UC Davis Health employees who received two doses of the Pfizer or Moderna COVID-19 vaccine more than five months ago are eligible for a booster shot. Additionally, employees who received a Johnson & Johnson vaccine can also get a booster shot two months after their initial dose. Employee Health Services is also offering flu vaccines for employees.

The UC Office of the President updated its COVID-19 vaccination policy to require all UC health care workers get a COVID-19 booster by Jan. 31.

Related: UC Office of the President announces that all UC employees must receive a COVID-19 booster

Protection against infection decreases over time. As a result, about 5 months after the initial COVID-19 vaccine, fully vaccinated people have more risk for breakthrough infections.

For people younger than 65 years of age and who don’t have underlying conditions that increase their risk of getting the virus, COVID-19 breakthrough infections are generally mild. Most of the time, these infections don't cause severe disease or hospitalization. Therefore, this group may choose a booster vaccine to decreased risk of breakthrough infection.

People 65 and older or those with underlying conditions are at higher risk for severe infection. A COVID-19 booster dose is recommended for these groups

For immunocompromised patients, the immune response to the first two doses of mRNA vaccine may not result in enough protection, so a third COVID-19 vaccine is recommended.

Side effects following a booster or third dose of COVID-19 vaccine are similar to side effects following the second dose, with slightly more pain at the injection site, fever, chills, and fatigue. No serious side effects were found in third dose studies.

On Oct. 21, the CDC updated its recommendations to allow for the mixing of COVID-19 vaccine boosters from different manufacturers. In other words, if you received your first two doses of Pfizer, the CDC’s recommendations allow for you to get a booster dose of the Moderna vaccine – or vice-versa.

UC Davis Health plans to match previous vaccine doses with the booster shot.

Experts don’t know yet how often additional COVID-19 vaccine doses will be needed. Data is needed to see how protection varies by specific vaccine and in different populations. This is likely to evolve as the pandemic evolves and may be impacted by the development of new variants.

It was understood that COVID-19 vaccines would not protect people forever. Although some vaccine manufacturers have publicly stated that they believe boosters are needed due to declining protection, there is very little data at this time that shows decreasing protection. So far, protection appears to be durable.

According to CDC data, the Moderna vaccine is 94.1% effective at preventing laboratory-confirmed COVID-19 infection in people who received two doses and had no evidence of being previously infected.

While the vaccines' effectiveness at preventing symptoms and illness declines over time as the body processes its immune response, all of the vaccines are still highly effective against hospitalization and death. These third doses of vaccine are aimed largely at preventing illness and reducing spread during the shorter time a vaccinated person may be ill. However, the initial two-dose series is still highly effective at preventing serious infections leading to hospitalization or death.

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