Master Class

Maternal immunization is a priority

Publish date: July 30, 2020

Other vaccines in pregnancy and post partum

As described in the American College of Obstetricians and Gynecologists’ committee opinion on maternal immunization,⁴ it is the responsibility of the ob.gyn. or obstetric care provider to routinely assess the immunization status of every pregnant patient and recommend additional vaccines for those patients who have conditions or social/behavioral practices that put them at higher risk of acquiring vaccine-preventable diseases.

Patients who have asthma or diabetes, who smoke, or who have never been vaccinated for the prevention of pneumococcal disease should receive the PPV23 pneumococcal vaccine, for instance. For pregnant women with immune deficiencies such as HIV, the PCV13 vaccine followed by PPV23 is recommended. There are approximately 500,000 cases of invasive pneumococcal disease in the United States each year, resulting in 40,000 deaths, and many multidrug-resistant strains of Streptococcus pneumoniae.

Hepatitis A and B vaccines – both recombinant vaccines with no safety concerns – also can be given during pregnancy and are officially recommended for women who have high-risk exposures. In the case of hepatitis A, high risk entails traveling to countries where the disease is endemic. High-risk behavior for hepatitis B includes sex work or being the household contact or sexual partner of a person positive for hepatitis B surface antigen.

Other travel-related vaccines, such as Japanese encephalitis, yellow fever, smallpox, and inactivated polio vaccine, can be considered in pregnancy, but decisions should be driven by more in-depth conversations about potential risks and benefits. Unlike for other vaccinations, there are limited data on the safety of travel-related immunizations in pregnancy. Sometimes, the question of whether travel is advisable in the middle of pregnancy – whether potential risks are worth taking – is a valid question to pose in conversations with patients.

Standard obstetric practice includes assessment of rubella susceptibility at the beginning of pregnancy. In some locations such as New York, measles susceptibility is also routinely evaluated. After delivery, seronegative women should be vaccinated with MMR (measles, mumps, and rubella) vaccine prior to discharge. In recent years, with the growing problem of vaccine refusal and an increasingly mobile and global society, we’re seeing sporadic outbreaks of measles and rubella – diseases that were once eradicated.

Measles in particular is highly contagious and requires a herd immunity threshold of 92%-94% to prevent sustained spread of the disease. Postpartum immunization has important maternal and pediatric implications for subsequent pregnancies, before which vaccination is often missed.

Both the MMR vaccine and the varicella vaccine (another vaccine that can be initiated post partum) are live vaccines and therefore contraindicated during pregnancy but should be administered post partum, including to people who are breastfeeding.

Other immunizations that hold some promise to protect either the mother or fetus/neonate or both are in various stages of development or testing. These include vaccines for cytomegalovirus, malaria, respiratory syncytial virus, and group B streptococcus.

A word about COVID-19

In mid-July there were more than 120 vaccine candidates for COVID-19 in various phases of study and a host of questions. Will a vaccine be efficacious? Will it prevent severe illness, or illness altogether? And will it be safe for pregnant women?

Vaccines work by manipulating the immune system, and it is important to appreciate the possibility that there may be unique pregnancy-related issues to consider with future COVID-19 vaccines – issues that could influence the effectiveness, safety, and timing of vaccination – and to understand that with any new immunization, there will likely be reluctance on the part of pregnant women who routinely prioritize fetal safety over their own health.

Pregnant women have been excluded from COVID-19 vaccine trials, but there may come a time when experts decide that a vaccine against COVID-19 is beneficial in pregnancy. Thus far, we know that the disease is clearly different from influenza. A growing knowledge of the impact of COVID-19 on the health of pregnant women, particularly the risk of developing severe illness, will be important for the future of COVID-19 immunization, as many women will not want to accept any potential risk of a vaccine unless they believe there is a significant benefit.