Immunization during pregnancy

Immunization during pregnancy is the administration of a vaccine to a pregnant individual. This may be done either to protect the individual from disease or to induce an antibody response, such that the antibodies cross the placenta and provide passive immunity to the infant after birth. In many countries, including the US, Canada, UK, Australia and New Zealand, vaccination against influenza, COVID-19 and whooping cough is routinely offered during pregnancy. Other vaccines may be offered during pregnancy where travel-related or occupational exposure to disease-causing organisms warrant this. However, certain vaccines are contra-indicated in pregnancy. These include vaccines that include live attenuated organisms, such as the MMR and BCG vaccines, since there is a potential risk that these could infect the fetus. Newborns are at increased risk of infection, particularly before they receive their first infant vaccinations. For this reason, certain vaccinations are offered during pregnancy in order to induce an antibody response, resulting in the passage of antibody across the placenta and into the fetus: this confers passive immunity on the newborn. As early as 1879, it was noted that infants born following smallpox vaccination in pregnancy were themselves protected against smallpox. However, the original smallpox vaccination was never widely used during pregnancy because, as a live vaccine, its use is contraindicated. Tetanus is a bacterial infection caused by Clostridium tetani. Newborns can be infected via their unhealed umbilical stump, particularly when the umbilical cord is cut with a non-sterile instrument, and suffer a generalised infection. The tetanus toxoid vaccine was first licensed for use in 1938 and, during the 1960s, it was noted that tetanus vaccination in pregnancy could prevent neonatal tetanus. Subsequent trials showed that vaccination of pregnant women reduces infant deaths from tetanus by 94%. In 1988, the World Health Assembly passed a resolution to use maternal vaccination to eliminate neonatal tetanus by the year 2000.