CDC Shares New Recommendations for Timing Between Vaccine Doses

The CDC recommends a longer interval between the first and second dose for people 12 and up, and recommends a shorter interval for fourth doses for the immunocompromised population.

COVID-19 Vaccine for 5-11 year olds given at Cook Children's

The Centers for Disease Control and Prevention updated recommendations this week for the spacing of COVID vaccines for people 12 and up and for people who are immunocompromised.

The CDC recommends a longer interval between the first and second dose for people 12 and up, and recommends a shorter interval for fourth doses for the immunocompromised population.

The CDC emphasized that COVID-19 vaccines have been a critical tool in this pandemic, preventing millions of COVID-19 associated hospitalizations and deaths. To date, hundreds of millions of doses of mRNA COVID-19 vaccines have been given with over a year of closely monitored real-world safety and effectiveness data, the CDC said.

There are known cases of myocarditis in a small number of people ages 18-39 believed due to the mRNA vaccines. Per million second doses administered, 33 cases were reported for Moderna and 24 for Pfizer, according to the CDC.

Second Dose Recommendations

Recent studies revealed that rates of myocarditis/pericarditis were lower with extended interval between first and second dose of mRNA vaccine primary series. Extended primary series interval may also improve immunogenicity and vaccine effectiveness.

Because of this, an eight-week interval for second doses may be optimal for some people ages 12 years and older, especially for males ages 12 to 39 years old, the CDC said.

“In a very tiny number of young people, especially males age 12-39, COVID mRNA vaccines can cause a mild inflammation of the heart muscle," says Pediatrician Diane Arnaout, M.D., of Cook Children’s Pediatrics Forest Park. "This is called myocarditis, and just means that the immune system got really worked up really quickly. Thanks to the ongoing and constant safety studies done on vaccines, this small tweak to the regimen will likely mean less incidents of an already rare problem.”

The CDC still recommends the shorter second-dose interval for people who are moderately or severely immunocompromised; adults 65 years and older; and others who need rapid protection due to increased concern about community transmission or risk of severe disease. That interval is three weeks for Pfizer-BioNTech and 4 weeks for Moderna after receiving your first dose.

The shorter interval is still recommended for:

People who are at higher risk of having an inadequate response to the first mRNA vaccine dose
People who are moderately or severely immunocompromised
Are at higher risk for severe COVID-19
Adults ages 65 years and older
Need rapid protection, such as during high levels of community transmission
Children ages 5–11 years

4th Booster Shots for Immunocompromised

People who are moderately or severely immunocompromised should receive a booster dose at least three months after the last (third) dose of an mRNA COVID-19 vaccine, the CDC said this week. Previously recommendations were set for at least five months.