Smallpox Vaccine and Pre-Pregnancy Planning: What to Do

Background - Why This Matters

Step-by-Step Approach for a Pre-Pregnancy Woman

1. Check Vaccination Status First

• Ask for her vaccination records or immunization card.
• Look for a take site scar on the upper arm - a characteristic pockmark scar from the bifurcated needle technique. The presence of a scar is strong (though not absolute) evidence of prior smallpox vaccination.
• Serology (vaccinia-specific antibody titres) can be checked if there is genuine clinical or occupational need, but this is not routinely recommended for the general population.

2. Is Vaccination Even Indicated?

• Laboratory workers who handle live orthopoxviruses (variola, vaccinia, monkeypox)
• Public health/healthcare emergency response team members designated to respond to a smallpox outbreak

3. If She IS in a High-Risk Occupation

• Smallpox vaccine is contraindicated in pregnancy (pre-event setting). This is a firm contraindication per the Red Book 2021 (Committee on Infectious Diseases, p. 1047) and CDC ACIP guidelines.
• Reason: Risk of fetal vaccinia - a rare but serious condition (roughly 50 cases ever reported worldwide) that can cause fetal/neonatal death or premature birth.
• Plan: She should receive smallpox vaccination before attempting conception, and must avoid pregnancy for at least 4 weeks after vaccination.
• Vaccinia virus has not been shown to be teratogenic itself, but the risk of fetal infection through the mother's bloodstream (fetal vaccinia) is the main concern.

4. Inadvertent Vaccination Scenario

• She should not automatically terminate the pregnancy - vaccinia virus has not been documented as teratogenic.
• She should be counseled about the (low but real) risk of fetal vaccinia.
• Enroll in the CDC Pregnancy Registry (contact 404-639-8253) for prospective follow-up.
• Vaccinia immune globulin (VIG) may be considered in consultation with CDC.

5. Post-Eradication Context and Vaccine Duration

• Protection from prior smallpox vaccination wanes over time - substantial immunity up to 15-20 years, but significant decline thereafter.
• If she had documentation of prior vaccination but it was decades ago, she would need a booster only if she falls in the high-risk occupational category above, and again, this should be done before conception with a 4-week buffer.

Summary Table

Key Points to Communicate to the Patient

1. Smallpox was eradicated - she is very unlikely to ever encounter it unless there is a deliberate release (bioterrorism) or major outbreak.
2. For most women planning pregnancy, smallpox vaccine is not on the pre-pregnancy checklist at all.
3. If her job requires vaccination, she should get it now, use contraception for 4 weeks, then proceed with pregnancy planning.
4. Other pre-pregnancy vaccines (MMR, varicella, Tdap, hepatitis B, flu, COVID-19) are far more relevant and should be reviewed at her pre-conception visit per ASRM 2024 vaccine guidelines.

• Red Book 2021 (Committee on Infectious Diseases), p. 1047 - Smallpox preexposure immunization and contraindications
• CDC Guidelines for Vaccinating Pregnant Women (2024) - Smallpox-specific recommendations
• ASRM Committee Opinion (2024) - Preconception vaccine recommendations

Chickenpox (Varicella) and Pregnancy Planning

Why This Is Important

• For the mother: Varicella pneumonia is significantly more severe in pregnant women - higher rates of hospitalization and mortality compared to non-pregnant adults.
• For the fetus: Primary maternal varicella before 20 weeks gestation carries ~1-2% risk of Congenital Varicella Syndrome (CVS) - which includes limb hypoplasia, skin scarring (cicatricial scarring), eye defects (chorioretinitis, cataracts), microcephaly, and neurological abnormalities. The risk is highest at 8-20 weeks gestation.
• Perinatal varicella: If maternal infection occurs within 5 days before to 2 days after delivery, the newborn can develop severe, disseminated neonatal varicella (up to 30% mortality if untreated).
• Fitzpatrick's Dermatology (Vol. 1-2), Complications of Varicella section
• Red Book 2021 (AAP Committee on Infectious Diseases)

Step-by-Step Management for This Woman

Step 1 - Assess Her Immunity Status

1. Written documentation of 2 doses of varicella vaccine
2. Laboratory confirmation (positive VZV IgG serology)
3. A reliable history of prior varicella disease (clinical diagnosis by a healthcare provider)

Step 2 - Interpret the Result

Step 3 - Vaccinate if Non-Immune (Before Pregnancy)

• Give 2 doses of varicella vaccine (live attenuated, Varivax) separated by 4-8 weeks
• Avoid pregnancy for at least 1 month (4 weeks) after the last dose - this is a firm guideline from CDC, ACOG, and ASRM
• The vaccine is a live attenuated virus, so it is contraindicated during pregnancy (based on theoretical risk of CVS, though inadvertent vaccination has NOT shown actual harm)
• Seroconversion (confirmed immunity) develops in ~95% of adults after 2 doses

"Those without evidence of immunity or previous infection should receive 2 doses of single-antigen varicella vaccine administered 1 month apart... Pregnancy should be avoided for 1 month after vaccination."

Step 4 - What If She Gets Pregnant Before Vaccination?

• Do NOT give varicella vaccine during pregnancy (contraindicated)
• Counsel her carefully about the risk of VZV exposure during pregnancy
• If she is exposed to chickenpox during pregnancy: administer Varicella-Zoster Immune Globulin (VZIG/VariZIG) within 96 hours of exposure to reduce severity
• After delivery and before hospital discharge: give first dose of varicella vaccine, then second dose 4-8 weeks later

Step 5 - Inadvertent Vaccination During Pregnancy

• Do not recommend termination - no causal link between varicella vaccine and congenital varicella syndrome has been established
• Counsel her about the theoretical (but not proven) risk
• Register with the VAERS / CDC vaccine-in-pregnancy registry for monitoring

Summary Flowchart

Woman planning pregnancy, unknown varicella status
            |
     Check VZV IgG serology
            |
   ┌────────┴────────┐
Positive (immune)   Negative/equivocal (non-immune)
   |                        |
No action needed     Give 2 doses varicella vaccine
Proceed with         4-8 weeks apart
pregnancy planning   WAIT ≥ 4 weeks after last dose
                     THEN attempt conception

Don't Forget These Other Pre-Pregnancy Vaccines

• MMR (Measles-Mumps-Rubella) - also live vaccine, avoid pregnancy for 1 month after
• Hepatitis B (if not immune)
• Tdap (tetanus, diphtheria, acellular pertussis)
• Influenza (can be given in pregnancy)
• COVID-19 (can be given in pregnancy)
• HPV (if applicable by age)