COVID-19 Vaccine Boosters Explained: what are they and who should get them?

The United States Centers for Disease Control and Prevention have authorized booster vaccinations for certain individuals who have received any of the three flavors of the COVID-19 vaccine. Based on different criteria, the CDC recommends that some people should receive a booster, some people can get a booster, and some people do not currently need one.

Booster shots are the same formula as the existing vaccines. They are exactly the same as receiving an additional dose of the vaccine, though Moderna boosters are half-size. The CDC authorized their implementation after data showed that over time the level of protection afforded by the vaccines diminished over time. CDC guidance maintains that protection against severe illness, hospitalization and death is holding, but the protections against mild illness can wane over time.

Booster shots are not only intended to counter diminishing protection by the vaccine but also to react to the greater infectiousness of the Delta variant. Because the virus is still effective at significantly reducing the risk of severe illness and death, boosters are currently only recommended for those who are considered at-risk for any of a variety of reasons.

For that reason, the CDC recommends that people who received both doses of either the Pfizer or Moderna mRNA vaccines receive boosters six months after their second dose if they are older than 65, if they live in long-term care facilities, or if they have underlying medical conditions. Boosters are also available to those individuals who work or live in high-risk settings like hospitals, schools, factories, prisons and grocery stores.

The CDC recommends that everyone who received the Johnson and Johnson vaccine receive a booster at least two months after their initial dose. The CDC website states that the J&J vaccine “has lower effectiveness over time than mRNA vaccines.”

The vaccines work by producing a harmless facsimile of the virus in the body, which is then targeted by the immune system, which creates antibodies tailored to attack COVID-19 cells.

The Moderna and Pfizer vaccines are mRNA vaccines, which contain instructions in the form of messenger RNA that teach the body to create a protein unique to COVID-19. The body produces this protein, then the mRNA dissolves completely. The immune system recognizes that protein as foreign and develops antibodies to attack it, a response that will be just as effective if a full COVID-19 cell shows up.

The Johnson and Johnson vaccine is a viral vector vaccine, which contains a modified, harmless, virus that enters the body and produces a spike protein that is found on COVID-19 cells. Though the method of delivery is different, it is functionally very similar to the mRNA vaccines in that the body will attack the proteins in the same way it will need to attack real COVID-19. Vaccines teach the body how to react so it doesn’t have to learn when the real infection comes.  

The CDC announced on Oct. 21 that mixing and matching vaccine types would be allowed for booster shots. This means that regardless of what vaccine any individual received for their original doses, any of the authorized vaccines can be applied as a booster. Those with both shots of Moderna could choose to stick to Moderna or receive Pfizer or J&J’s as the supplement. There is no indication at this time that mixing and matching vaccines provide any difference in effectiveness, this change was simply made to promote the availability of vaccines and boosters.

Most providers offer walk-in vaccine appointments at this time. Individuals looking to find vaccines available in their area can use vaccines.gov to find doses anywhere in the country, or anchoragecovidvaccine.org to view doses in Anchorage specifically.