On Friday, Feb. 11, the Centers for Disease Control and Prevention (CDC) updated its COVID-19 vaccine guidance for people who are moderately or severely immunocompromised. The new guidance reduces the wait time for a booster (fourth) dose of an mRNA vaccine (Moderna or Pfizer) from five months to three months in immunocompromised people. In other words, if you are immunocompromised and got your third dose more than three months ago, it’s time for your booster.

For immunocompromised recipients of the Johnson & Johnson vaccine, the CDC recommends an additional dose of an mRNA vaccine at least 28 days after the initial dose, then a booster dose two months later. (The booster dose can be any of the three vaccines, but mRNA is preferred.) For specific guidance on additional and booster doses for immunocompromised people who received the Johnson & Johnson primary vaccine, visit this CDC webpage.

For children ages 5-11 with compromised immunity the CDC recommends an additional (third) dose of the Pfizer vaccine, but as of this time a booster (fourth) dose is not authorized.

In people who are immunocompromised, a primary vaccine series may not be enough to strengthen the immune system. That’s why immunocompromised people were advised last year to get a third primary series dose of an mRNA vaccine. “The more one is exposed to a virus, or to an important viral protein, the better able your immune system is to fight it off,” said Dr. Paul Cieslak, medical director for communicable diseases and immunizations at Oregon Health Authority. “That additional dose often gives the immune system the extra push it needs.”

The CDC then advised a fourth dose, or booster, for immunocompromised people. Small studies in immunocompromised individuals have shown that when a booster dose is given one to three months after completion of the three-dose primary vaccine series, the immune system responds quite well, according to the CDC.

 “A booster dose can bump your immune response back up to where it was – or even higher,” Cieslak said. “The data show that this is especially important with the Omicron variant.”

Cieslak recommends that in addition to being vaccinated and boosted, people who are immunocompromised should practice good hand hygiene, stay away from people who are ill and avoid risky foods such as undercooked meats, eggs or shellfish.

“Ask your loved ones and anyone you spend a lot of time with to get vaccinated, too!” Cieslak said.

People are considered to be moderately or severely immunocompromised if they are:

• Receiving active cancer treatment
• Organ transplant recipients and taking medicine to suppress the immune system
• Stem cell transplant recipients (within the last two years) who are taking medicine to suppress the immune system
• Diagnosed with moderate or severe primary immunodeficiency (such as DiGeorge syndrome or Wiskott-Aldrich syndrome)
• Experiencing advanced or untreated HIV infection
• Receiving active treatment for conditions that require high doses of corticosteroids or other drugs that may suppress your immune response

People should talk to their healthcare provider about their medical condition and whether getting an additional primary shot is appropriate.

On a case-by-case basis, providers who care for moderately or severely immunocompromised patients may administer mRNA COVID-19 vaccines outside of the FDA and CDC dosing intervals based on clinical judgment when the benefits of vaccination would outweigh the potential and unknown risks.