Guidance on CDC’s Interpretation of vaccination records (when mixing of mRNA, adenoviral, and mRNA plus adenoviral products)

In general, people are considered fully vaccinated:

  • 2 weeks after their second dose in a 2-dose series, such as the Pfizer-BioNTech or Moderna vaccines, or
  • 2 weeks after a single-dose vaccine, such as Johnson & Johnson’s Janssen vaccine

This guidance applies to COVID-19 vaccines currently approved or authorized for emergency use by the U.S. Food and Drug Administration (Pfizer-BioNTech, Moderna, and Johnson & Johnson [J&J]/Janssen COVID-19 vaccines), and can be applied to COVID-19 vaccines that have been listed for emergency use by the World Health Organization (such as AstraZeneca/Oxford). Additionally, this guidance can be applied to clinical trial participants from U.S. sites who received all recommended doses of a COVID-19 vaccine that is neither approved nor authorized for use by FDA but is listed for emergency use by WHO, or who have received the full series of an “active” (not placebo) COVID-19 vaccine candidate for which vaccine efficacy has been independently confirmed (e.g., by a data and safety monitoring board). Currently, participants in the U.S.-based AstraZeneca and Novavax COVID-19 vaccine trials meet these criteria. These U.S. participants in COVID-19 vaccine trials can be considered fully vaccinated 2 weeks after they complete the vaccine series, if it has been confirmed that they received “active” vaccine, and not placebo. More information is available at Interim Clinical Considerations for Use of COVID-19 Vaccines | CDC.

Interpretation of vaccine records: CDC has not recommended the use of heterologous (i.e., mix-and-match) primary series. However, the use of such strategies (including mixing of mRNA, adenoviral, and mRNA plus adenoviral products) is increasingly common in many countries outside of the United States. Therefore, for the purposes of interpretation of vaccination records, individuals can be considered fully vaccinated ≥2 weeks after receipt of the last dose if they have received any single dose of an FDA approved/authorized or WHO EUL approved single-dose series (i.e., Janssen), or any combination of two doses of an FDA approved/authorized or WHO emergency use listed COVID-19 two-dose series.  The recommended interval between the first and second doses of FDA-approved/authorized and WHO-EUL listed vaccines varies by vaccine type. However, for purposes of interpretation of vaccine records, the second dose in a two dose heterologous series must have been received no earlier than 17 days (21 days with a 4 day grace period) after the first dose. The above guidance on interpreting vaccine records does not impact CDC recommendations on primary series vaccination and should not guide clinical practice.

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