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How many doses do I need of the vaccines? (UPDATED*)

Pfizer-BioNTech and Moderna Vaccines

The mRNA vaccines come in two doses. The first dose of the vaccine helps prepare your immune system and the second dose provides most of the immunity. Once you receive both doses of the vaccine, it will likely take several weeks for your body to develop immunity. Both doses are important to ensure full protection.

  • People receiving the Pfizer-BioNTech vaccine will need a second dose 21 days after the first, while those who get the Moderna vaccine will need a booster 28 days later.
  • Persons should not be scheduled to receive the second dose earlier than recommended (i.e., three weeks [Pfizer-BioNTech] or one month [Moderna]). However, second doses administered within a grace period of four days earlier than the recommended date for the second dose are still considered valid. Doses inadvertently administered earlier than the grace period should not be repeated.
  • The second dose should be administered as close to the recommended interval as possible. However, if it is not feasible to adhere to the recommended interval, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be scheduled for administration up to six weeks (42 days) after the first dose. There are currently limited data on efficacy of mRNA COVID-19 vaccines administered beyond this window. If the second dose is administered beyond these intervals, there is no need to restart the series.

Booster Shots

Booster shots for the mRNA vaccines will soon be available.

On 8/18, HHS put out the following statement:

We are prepared to offer booster shots for all Americans beginning the week of September 20 and starting 8 months after an individual’s second dose. At that time, the individuals who were fully vaccinated earliest in the vaccination rollout, including many health care providers, nursing home residents, and other seniors, will likely be eligible for a booster. We would also begin efforts to deliver booster shots directly to residents of long-term care facilities at that time, given the distribution of vaccines to this population early in the vaccine rollout and the continued increased risk that COVID-19 poses to them.

Additional Dose for Immunocompromised Patients

The CDC recommends people who are moderate to severely immunocompromised should receive an additional dose of mRNA COVID-19 vaccine after the initial 2 doses.

  • This additional dose intended to improve immunocompromised people’s response to their initial vaccine series is not the same as a booster dose, given to people when the immune response to a primary vaccine series is likely to have waned over time.
  • CDC does not recommend additional doses or booster shots for any other population at this time.
  • CDC recommends that people with moderately to severely compromised immune systems receive an additional dose of mRNA COVID-19 vaccine at least 28 days after the second dose of Pfizer-BioNTech or Moderna vaccine

Currently, CDC is recommending that moderately to severely immunocompromised people receive an additional dose. This includes people who have:

  • Been receiving active cancer treatment for tumors or cancers of the blood
  • Received an 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

People should talk to their healthcare provider about their medical condition, and whether getting an additional dose is appropriate for them.

 

Sources

Updated: August 24, 2021

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