CDC Modifies Interval Time Between Dosing for mRNA COVID-19 Vaccines to 6 Weeks

The Centers for Disease Control and Prevention (CDC) has modified the recommendations of the intervals of dosing between the first and second doses of the mRNA COVID-19 vaccines up to 6 weeks, if their current dosing recommendations cannot be met.

“The second dose should be administered as close to the recommended interval as possible,” the CDC wrote on its site. “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 6 weeks (42 days) after the first dose.”

CDC said there is limited data on the efficacy of these vaccines beyond that timeframe.

While the agency did not offer specific reasoning for the change it may be due to supply shortages or the Biden administration’s goal to achieve 100 million vaccinations in the first 100 days in office. This new goal would need to be met on April 30.

It has been recently noted the states have been complaining of vaccine shortages. Last week, Oregon Governor Kate Brown shared via Twitter her discussion with Operation Warp Speed Chief Operation Officer Gen. Gustave Perna on the matter.

“States will not be receiving increased shipments of vaccines from the national stockpile next week, because there is no federal reserve of doses,” Brown said.

In the updated guidance, CDC made it clear to follow the recommended dosing schedules for the Moderna (28 days apart) and the Pfizer-BioNtech (21 days apart) vaccines when possible.

Interchangeability of the mRNA Vaccines

In addition, the CDC also covered the interchangeability of the mRNA vaccine products. They made it clear it was important to receive the same vaccine product for the 2 doses.

“These mRNA COVID-19 vaccines are not interchangeable with each other or with other COVID-19 vaccine products,” the CDC wrote on their site. “The safety and efficacy of a mixed-product series have not been evaluated. Both doses of the series should be completed with the same product.”

In order to ensure people are receiving the second dose of the same vaccine, the agency offered some strategies, which include the following:

• Providing COVID-19 vaccination record cards to vaccine recipients, asking recipients to bring their card to their appointment for the second dose, and encouraging recipients to make a backup copy (e.g., by taking a picture of the card on their phone).
• Encouraging vaccine recipients to enroll in VaxTextSM, a free text message-based platform to receive COVID-19 vaccination second-dose reminders.
• Recording each recipient’s vaccination in the immunization information system (IIS).
• Recording vaccine administration information in the patient’s medical record.
• Making an appointment for the second dose before the vaccine recipient leaves, to increase the likelihood that patients will present at the same vaccination site for the second dose.