Pregnancy and Breastfeeding Risk Categories: Vaccines

Smallpox Vaccine

From Anthrax to Yellow Fever, learn about the safety of the most common vaccines during pregnancy and breastfeeding with the following general overview of vaccines.

VaccinePregnancy Risk CategoryBreastfeeding Risk Category
Anthrax VaccineCL3
Cholera Vaccine
Diphtheria + Tetanus + Pertussis Vaccine
Diphtheria + Tentanus Vaccine
(DT, Td, Decavac)
Diphtheria VaccineCL3
Haemophilus B Conjugate Vaccine
(HibTITER, Haemophilus B Vaccine, ProHIBiT, OmniHIB, Act-HIB, PedvaxHIB, Hib Titer)
Hepatitis A + Hepatitis B Vaccine
Hepatitis A Vaccine
(Havrix, Vaqta)
Hepatitis B Vaccine
(Heptavax-B, Energix-B, Recombivax HB)
Human Papillmoavirus Vaccine
(Gardasil, Cervarix, HPV Vaccine)
Influenza Virus Vaccines
(Flu Shot, Influenza Vaccine, Flu-Imune, Fluogen, Fluzone, FluMist, Flu Vaccine)
Japanese Encephalitis Vaccine
(Encephalitis Vaccine)
Lyme Disease Vaccine
Measles + Mumps + Rubella Vaccine
(MMR Vaccine, M-M-R II, ProQuad, Priorix)
Measles + Mumps + Rubella + Varicella Vaccine
(ProQuad, MMRV Vaccine)
Measle Virus Vaccine, Live
(MMR, Attenuvax)
Meningococcal Vaccine
(Menomune, Menveo, Menactra)
Mumps Virus Vaccine, Live
(MMR, Mumpsvax)
Pertussis VaccineCL2
Pneumococcal Vaccine
(Prevnar, Pneumovax 23, Pneuno 23, Pneumovax 23)
Polio Vaccine, Inactivated
Polio Vaccine, Oral
(Vaccine-Live Oral Trivalent Polio)
Quadrivalent Human Papillmoavirus Vaccine
Rabies Vaccine
(Imovax Rabies Vaccine. RabAvert)
Rubella Virus Vaccine, Live
(Meruvax, Rubella Vaccine, Measles Vaccine)
Smallpox Vaccine
Tetanus Toxoid Vaccine
(TE Anatoxal Berna)
Typhoid Vaccine
(Vivotif Berna, Typhim Vi)
CL3 (injectable)
Varicella Virus Vaccine
(Varivax, Chickenpox Vaccine, Varicella Vaccine)
Varicella-Zoster VaccineHazardousL4
Yellow Fever Vaccine
(YF-Vax, Arilvax, Stamaril)
Zoster Vaccine, Live


Pregnancy Risk Categories

A. Controlled Studies Show No Risk

Adequate, well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester of pregnancy.

B. No Evidence of Risk in Humans


Adequate, well-controlled studies in pregnant women have not shown increased risk of fetal abnormalities despite adverse findings in animals, or, in the absence of adequate human studies, animal studies show no fetal risk. The chance of fetal harm is remote but remains a possibility.

C. Risk Cannot Be Ruled Out

Adequate,well-controlled human studies are lacking, and animal studies have shown a risk to the fetus or are lacking as well. There is a chance of fetal harm if the drug is administered during pregnancy, but the potential benefits may outweigh the potential risks.


D. Positive Evidence of Risk

Studies in humans, or investigational or post-marketing data, have demonstrated fetal risk. Nevertheless, potential benefits from the use of the drug may outweigh the potential risk. For example, the drug may be acceptable if needed in a life-threatening situation or serious disease for which safer drugs cannot be used or are ineffective.

X. Contraindicated in Pregnancy

Studies in animals or humans, or investigational or post-marketing reports, have demonstrated positive evidence of fetal abnormalities or risks which clearly outweighs any possible benefit to the patient.

Breastfeeding Risk Categories

L1. Safest

Drug which has been taken by a large number of breastfeeding mothers without any observed increase in adverse effects in the infant. Controlled studies in breastfeeding women fail to demonstrate a risk to the infant and the possibility of harm to the breastfeeding infant is remote, or the product is not orally bioavailable in an infant.

L2. Safer

Drug which has been studied in a limited number of breastfeeding women without an increase in adverse effects in the infant; and/or, the evidence of a demonstrated risk which is likely to follow use of this medication in a breastfeeding woman is remote.

L3. Moderately Safe

There are no controlled studies in breastfeeding women; however, the risk of untoward effects to a breastfed infant is possible; or, controlled studies show only minimal non-threatening adverse effects. Drugs should be given only if the potential benefit justifies the potential risk to the infant.

L4. Possibly Hazardous

There is positive evidence of risk to a breastfed infant or to breastmilk production, but the benefits of use in breastfeeding mothers may be acceptable despite the risk to the infant (e.g. if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).

L5. Contraindicated

Studies in breastfeeding mothers have demonstrated that there is significant and documented risk to the infant based on human experience, or it is a medication that has a high risk of causing significant damage to an infant. The risk of using the drug in breastfeeding women clearly outweighs any possible benefit from breastfeeding. The drug is contraindicated in women who are breastfeeding an infant.

Disclaimer: The information provided in this article is not meant to replace the professional medical advice from your health care provider. For detailed information on specific medications or for information on medications not listed, please consult your health care provider.


Hale, Thomas W. 2008. Medications and mothers’ milk, 13th edn. Amarillo, Texas: Hale Publishing.
Hale, Thomas W. 2010. Medications and mothers’ milk, 14th edn. Amarillo, Texas: Hale Publishing.
Hale, Thomas W. 2012. Medications and mothers’ milk, 15th edn. Amarillo, Texas: Hale Publishing.
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Written by Heather Johnson

Heather is a writer, librarian, linguist, wife, and mother who loves her husband, children, dogs, and cats. She has a bachelor's degree in English with a minor in creative writing and master's degrees in library and information science and English studies with a concentration in linguistics.

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