Table 1.

COVID-19 vaccines (as of January 2023).

Vaccine mechanisma	Manufacturer	Interval between 1st and 2nd dose (primary series)	Interval between primary series and booster dose	Recommended bivalent booster	Possible side effects during lactation	Considerations
mRNA	Pfizer-BioNTech Moderna	3–8 weeks 4–8 weeks	≥2 months ≥2 months	Pfizer or Moderna	Milk production decrease (short-term), discoloration of milk; child irritability/poor sleep	1st line recommendation from CDC
Adenovirus vectorb	Janssen-Johnson & Johnson	n/a	≥2 months	Pfizer or Moderna	–	Only recommended in limited situationsc
Synthetic S protein (plus adjuvant)	Novavax	3–8 weeks	≥2 months	Pfizer or Moderna	–

^aThough current FDA-approved vaccine options in the US employ one of these mechanisms, there are several vaccines available outside the US that use an inactivated whole virus vaccine (such as those manufactured by Bharat Biotech, Sinopharm, and Sinovac).

^bAdditional adenovirus vector vaccines available outside the US include those manufactured by AstraZeneca, Sputnik-V, and CanSino; lactation-specific data are limited for these options.

^cCDC only recommends Janssen (Johnson & Johnson) in certain limited circumstances due to risk of thrombosis with thrombocytopenia (TTS); limited circumstances include having a contraindication to mRNA vaccines and Novavax, situations in which individual would otherwise not be vaccinated, and strong patient preference despite explanation of TTS risks.