Information on third and booster vaccine doses

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Boosters - Pfizer and Moderna

Based on guidance from the Centers for Disease Control and Prevention, those who meet the follow criteria and received the Pfizer/BioNTech or Moderna vaccine are eligible to receive booster shot at least six months after their second dose was administered:

• people 65 years and older and residents in long-term care settings

• people aged 18–64 years with underlying medical conditions

• people aged 18-64 years who are at increased risk for COVID-19 exposure and transmission because of occupational or institutional setting (e.g., frontline medical workers, teachers, and first responders)

Of those who are eligible, Missouri Department of Health and Senior Services strongly recommends that those age 65 and older, age 50–64 with underlying medical conditions, and all residents of long-term care facilities receive a booster shot six months after their second dose of the Pfizer/BioNTech vaccine. The list of medical conditions categorized as high-risk by the CDC is available here.

Boosters - Johnson & Johnson

The CDC states that everyone 18 and older who received the one-dose Johnson & Johnson vaccine should get a booster shot at least two months after their vaccine was administered.

Mixing Vaccine Types

While it is recommended that the same vaccine be administered, mixing vaccine types was also approved for the booster doses only. Individuals who are eligible to receive a booster shot can choose a different vaccine type than they received initially. Those with additional questions or in need of guidance should discuss their options with their healthcare provider.

Third Doses

On August 13, 2021, the Centers for Disease Control and Prevention recommended that moderately to severely immunocompromised people receive a third dose of the Pfizer-BioNTech or Moderna mRNA COVID-19 vaccines at least 28 days after their second dose. The same mRNA vaccine administered for the first and second doses should be used for the third dose.  

Per CDC guidance, individuals who should receive a third dose include those who have: 

  • Active cancer treatment for solid tumors or cancers of the blood 
  • Received a solid organ transplant and are taking medicine to suppress the immune system 
  • Received a stem cell transplant (within the last 2 years or are taking medicine to suppress the immune system) 
  • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome) 
  • Advanced or untreated HIV infection 
  • Active treatment with high-dose corticosteroids or other drugs that may suppress your immune response 

Individuals should talk to their healthcare provider about their medical condition, and whether getting an additional dose is appropriate for them. Although hospitalizations and fatalities among fully vaccinated individuals are rare, data from the CDC suggests that immunocompromised individuals may have a reduced response to the COVID-19 vaccination, leaving them more susceptible to illness. 

At this time, the CDC’s recommendation does not apply to the Johnson & Johnson/Janssen COVID-19 vaccine, as there is not enough data to determine whether immunocompromised people who received the J&J vaccine have an improved antibody response following an additional dose of the same vaccine. 

Third dose mRNA boosters for all other individuals are currently under review by the CDC, FDA and ACIP.  

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