What is the optimal timing for a mother to receive her Covid (Coronavirus) and influenza vaccines to transfer maximum passive immunity to her four-month-old baby, and should it be spaced out from the baby's four-month vaccines?

Optimal Timing for Maternal COVID-19 and Influenza Vaccination to Maximize Passive Immunity Transfer

Mothers should receive both COVID-19 and influenza vaccines during the second or third trimester of pregnancy, at least 2 weeks before delivery, to maximize passive antibody transfer to their 4-month-old infant. 1, 2

Timing of Maternal Vaccination

• Maternal influenza vaccination during the second or third trimester, at least 15 days before delivery, provides optimal seroprotection to newborns through transplacental antibody transfer 2
• Studies show that maternal antibody titers in cord blood are significantly higher when mothers are vaccinated in either the second or third trimester compared to unvaccinated mothers 1
• Vaccination less than 4 weeks before birth results in significantly lower antibody levels in cord blood, though still higher than in infants of unvaccinated mothers 1
• For maximum protection, maternal influenza vaccination should be administered as soon as the seasonal vaccine becomes available, ideally by the end of October 3
• Pregnant women in their third trimester can receive influenza vaccination during July and August because this might reduce the risk of influenza illness in their infants during the first months after birth 3

Effectiveness of Maternal Vaccination for Infant Protection

• Maternal immunization boosts the concentration of maternal antibodies that transfer across the placenta to directly protect infants too young to be immunized 4
• Vaccinated pregnant mothers pass IgG antibodies to their offspring through transplacental transfer, with one study showing that transplacental transfer is more likely if the mother is vaccinated in the third trimester 3
• Infants born to mothers vaccinated against influenza during pregnancy have a risk reduction of 72% for laboratory-confirmed influenza hospitalization in the first few months of life 3
• Sustained high levels of influenza-specific IgA antibodies have been found in the breast milk of women vaccinated against influenza during pregnancy for up to 6 months after birth 3

Spacing Between Maternal and Infant Vaccinations

• There is no need to space out the timing between maternal vaccination and the infant's 4-month vaccines 5
• COVID-19 and influenza vaccines can be administered simultaneously to the mother at different anatomic sites 5, 6
• The infant's 4-month vaccines should proceed as scheduled regardless of when the mother receives her vaccines 3, 5
• Inactivated vaccines generally do not interfere with the immune response to other inactivated vaccines or to live vaccines in most cases 5

Vaccine Safety Considerations

• Inactivated influenza vaccines are considered safe for pregnant women and their fetuses 4
• Live attenuated influenza vaccines are contraindicated during pregnancy due to the theoretical risk of placental transmission of the virus to the fetus 3
• COVID-19 vaccines are considered safe during pregnancy, with initial safety data supporting the use of mRNA vaccines in pregnant women 3
• Pregnant women can receive inactivated influenza vaccines at any time during pregnancy to protect themselves and their infants 7

Practical Recommendations

• The mother should receive both influenza and COVID-19 vaccines as soon as they are available, ideally by the end of October 3, 6
• Both vaccines can be administered simultaneously at different anatomic sites to improve vaccination coverage and efficiency 5, 6
• If administering vaccines with increased reactogenicity (e.g., adjuvanted or high-dose influenza vaccines) along with COVID-19 vaccines, they should be injected into different limbs 5, 6
• The infant should continue to receive their scheduled 4-month vaccines without delay 3, 5

Common Pitfalls to Avoid

• Delaying vaccination to administer vaccines separately when they can be given simultaneously may lead to missed opportunities for vaccination 5
• Waiting too long to vaccinate the mother may result in insufficient time for optimal antibody transfer to the infant before birth 1, 2
• Vaccinating too close to delivery (less than 2 weeks before) results in suboptimal antibody transfer to the infant 1, 2
• Unnecessarily postponing the infant's 4-month vaccines due to concerns about interaction with maternal vaccination is not supported by evidence 5