The publication of this special edition “Immunisation in pregnancy” is timely. On 11 March 2020, the World Health Organization (WHO) declared the COVID-19 Pandemic, caused by the novel strain of the Coronavirus SARS-CoV-2. Eighteen months on, and at the time of going to press, over 220 million confirmed cases with over 4.5 million deaths have been reported worldwide. The pandemic has led to significant strain on the hospital systems and severe socioeconomic impact in every country of the world. This started the race to develop strategies to combat the virus and effects of the disease. The mainstay of this preventative strategy is the development of a safe and effective vaccine against the virus. Phase I clinical trials were commenced in April 2020. As of February 2021, at least seven different vaccines across three platforms have been rolled out in different countries across the world.
Vaccine development is a traditionally long, complex process, often lasting 10-15 years and commitment of a combination of public and private involvement and also regulatory processes. The tremendous collaborative efforts between scientists, with the support from governments have shown that the rapid development, clinical trials and logistical delivery of the vaccines are possible to help to bring this pandemic under control.
Several different platforms have been used to develop the COVID-19 vaccine. Although there are currently over 300 candidate vaccines at different phases of development, the types of vaccines are as follows: whole virus, protein subunit, viral vector and nucleic acid (RNA and DNA).
Whilst the benefits of vaccination are clear, the lack of clinical trials of the vaccine in pregnancy initially raised concerns about the safety profile of the COVID-19 vaccines in pregnancy and breastfeeding. However, emerging evidence from mass vaccination programmes in the United States of America and Israel have not shown any negative effects on fertility, conception, pregnancy and breastfeeding. On the basis of the safety information, the advice from the Centers for Disease Control and Prevention (CDC) in the United States, the Joint Committee on Vaccination and Immunisation in the United Kingdom (JCVI), World Health Organization (WHO) and many other medical regulatory bodies around the world now encourage pregnant women in all gestations, and those planning a pregnancy to be immunised against the COVID-19 virus.
Although the current focus is on COVID-19, we must not forget that other vaccine-preventable infectious diseases are responsible for significant maternal, neonatal and young infant morbidity and mortality worldwide. Ideally women should be vaccinated against preventable diseases in their environment before pregnancy. When immunisation is performed during pregnancy the benefits to the mother and the fetus should outweigh the risks. The physiological and immunological changes in pregnant women make them susceptible to certain infections and increase the risk of more serious outcomes. The immature adaptive immune systems of neonates and premature infants make them vulnerable to morbidity and mortality due to infection. Immunisation of pregnant women can protect them directly against vaccine-preventable infections, and in doing so potentially protect the fetus and infant via specific antibodies transferred from the mother during the pregnancy.
This edition covers a wide range of important topics relevant to immunisation in pregnancy. Readers will have a good understanding of the history of development of vaccines, the immunological changes in pregnancy to explain the susceptibility pregnant women, the fetus and infants to diseases. The lessons learned from the previous pandemics, the evidence behind the current vaccines, strategies to increase the uptake and the potential future vaccines in pregnancy provide readers an excellent wealth of knowledge in this very important aspect of preventive health to reduce the burden of disease in mothers and infants around the world.