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covid molecule


What is it?

COVID-19 is a disease caused by SARS-CoV-2.

SARS stands for severe acute respiratory syndrome. CoV means coronavirus, which is a family of viruses. 

Common symptoms include fever, chills, cough, loss of taste or smell, fatigue (tiredness), difficulty breathing, and muscle aches.

What's the difference between them?

Pfizer and Moderna are mRNA vaccines, while Johnson and Johnson and Novavax are viral vector vaccines.

For information about these types of vaccines, click here.

Pfizer and Moderna are recommended for people as young as 6 months old. Novavax is approved for ages 12+. Johnson and Johnson is approved for people over 18. 

Primary series:

  • The mRNA vaccines and Novavax require 2 doses, and Johnson and Johnson requires 1 dose. 

    • 3-8 weeks between doses for Pfizer​ and Novavax

    • 4-8 weeks between doses for Moderna

  • For kids under 5:

    • The Pfizer vaccine requires a 3-dose series with 3-8 weeks between dose 1 and 2 and at least 8 weeks between dose 2 and 3. 

    • Moderna is a 2-dose series with at least 4-8 days between doses

There are also booster doses:

  • Children as young as 6 months are eligible to receive a bivalent COVID-19 booster.

    • Bivalent means that it protects against 2 different versions of SARS-CoV-2 – the original strain and omicron (BA.4 and BA.5)

    • People are eligible for this booster if it has been at least 2 months since their last dose

    • There is not a specific recommendation for how long to wait to get a booster after COVID-19 infection, but some experts say that you should wait 4-6 months after infection (or a previous vaccine dose) before getting a booster.

Relevant Terms

  • mRNA: Messenger ribonucleic acid (mRNA) is a form of genetic material that acts as a template to make proteins.

  • Viral vector: a version of a virus that has been modified to contain genetic information from another source (in this case, the genetic information to make the spike protein). 

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