The Ministry of Health Singapore strongly recommends influenza and pertussis vaccination in pregnancy, in line with international guideline recommendations from the United Kingdom, the United States and other countries.

In 2017, the Ministry extended the use of Medisave for vaccines under the National Adult Immunisation Schedule, which include the vaccines against influenza and pertussis.

INFLUENZA VACCINATION IN PREGNANCY

INTRODUCTION

Influenza is a highly infectious respiratory viral illness that is transmitted from person to person via respiratory droplets propelled by coughing and sneezing, or via contact with contaminated surfaces.

The contagious period is from 1 day before the onset of symptoms till 5 to 7 days after onset. Common symptoms include fever, headache, chills, cough, sore throat, muscle aches, generalised malaise and fatigue.

Locally in Singapore, influenza is commonly seen, with between 1,500 and 3,500 people experiencing influenza-like illness every week. While most infected people will recover within 1 to 2 weeks, pregnant women, at any stage of pregnancy, are more likely to develop severe illness and are therefore at a higher risk of morbidity, and even mortality.

IMPACT OF INFLUENZA ON THE FETUS/NEONATE

• Potential increased risk of congenital abnormalities in the first trimester of pregnancy
• Maternal hyperthermia may increase the risk of certain birth defects
• Increased risk of obstetric complications, such as spontaneous abortion, preterm delivery, low birth weight and fetal death
• Infants less than 6 months old (neonates) infected with the influenza virus have the highest rates of hospitalisation and mortality compared to children of other older age groups

BENEFITS OF ANTENATAL INFLUENZA VACCINATION

• Reduces the risk of serious maternal medical complications
• Provides passive protection to the neonate via trans-placental transmission of antibodies (especially since the influenza vaccine cannot be administered for infants less than 6 months old)

INFORMATION ON THE INACTIVATED INFLUENZA VACCINE

• The inactivated influenza vaccine is safe in all trimesters of pregnancy, with studies conducted by the Centre for Disease Control and Prevention of the United States showing no evidence of a link between influenza vaccination administration and pregnancy complications or adverse fetal outcomes.
• The vaccine is administered as a single dose; repeated yearly with an updated vaccine.
• Common side effects experienced after an influenza vaccination include soreness, redness or swelling at the injection site from the shot, fainting, headache, fever, muscle aches, nausea and fatigue. If these side effects occur, they usually begin soon after the shot is administered and can last for about 1 to 2 days.
• Rarely, influenza vaccines can cause serious problems such as severe allergic reactions. People who have had a severe allergic reaction (e.g., anaphylaxis) after a previous dose, or a severe allergy to any of the vaccine components, should abstain from getting the vaccine.

PERTUSSIS VACCINATION IN PREGNANCY

INTRODUCTION

Pertussis, also known as whooping cough, is a highly contagious respiratory disease caused by the bacterium Bordetella pertussis. It is transmitted from person to person usually via coughing or sneezing, or via close contact in an enclosed environment.

Symptoms usually develop within 5 to 10 days after exposure, but sometimes not for as long as 3 weeks. Pertussis has an insidious onset with catarrhal symptoms and intermittent cough.

There has been an increase in the number of reported cases of pertussis worldwide since the 1980s.

RATIONALE FOR PREGNANT WOMEN TO UNDERGO TDAP VACCINATION

Pregnant women are encouraged to undergo vaccination against tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap).

The main aim of the antenatal Tdap vaccination is to provide passive protection to the neonate/infant via trans-placental transmission of antibodies (especially since the Tdap vaccine can only be administered to infants from 2 months of age).

Unvaccinated or incompletely vaccinated infants who are less than 12 months of age have a high risk of severe illness. Infants with pertussis who need treatment in hospital have an approximately 61% risk of apnoea, 23% risk of pneumonia, 1.1% risk of seizures, 1% risk of death and 0.3% risk of encephalopathy.

Vaccination is recommended with each pregnancy to provide maximal protection to every infant, as vaccineinduced pertussis antibodies wane over time and the protective antibody levels required in newborn infants is unknown.

INFORMATION ON THE TDAP VACCINE

• The Tdap vaccine is safe for use in pregnancy, with studies showing no link between Tdap vaccine administration and increased risk of pregnancy complications, such as low birth weight or preterm delivery.
• The vaccine is administered as a single dose intramuscularly, preferably at the deltoid area, between the 16th to 32nd week of each pregnancy.
• Maternal immune response to the vaccine peaks at about 2 weeks after administration.
• Common side effects experienced after a Tdap vaccination include erythema, swelling, pain and tenderness at the injection site, body ache, fatigue and fever.
• Rarely, Tdap vaccines can cause serious problems such as severe allergic reactions. People who have had a severe allergic reaction (e.g., anaphylaxis) after a previous dose, or a severe allergy to any of the vaccine components, should not receive the vaccine.

GPs can call for appointments through the KKH Central Appointments Hotline at 6294 4050 for more information.

Dr Serene Thain is an Associate Consultant with the Division of Obstetrics and Gynaecology, KK Women’s and Children’s Hospital. She received her undergraduate medical degree from the Yong Loo Lin School of Medicine in 2010, and obtained postgraduate degrees in Surgery in 2013 and Internal Medicine in 2014. In 2015, she was awarded the MRCOG Prize Medal for being the overall highest scoring candidate, and the 4th Asia-Oceania Congress of O&G Gold Medal for the Master of Medicine (Obstetrics & Gynaecology) examinations.

Dr Thain is a clinical tutor for Yong Loo Lin School of Medicine, Lee Kong Chian School of Medicine and Duke-NUS Medical School. She is also an active council member of the Obstetrics & Gynaecological Society, Singapore, and a journal reviewer for the Singapore Journal of Obstetrics and Gynaecology.

Dr Thain is pursuing subspecialty training in the field of Maternal Fetal Medicine. Her focus and interest within the subspecialty is that of Obstetric Medicine, which deals with the management and optimisation of high-risk pregnancies of women with complex medical conditions.

As Head of the Department of Maternal Fetal Medicine at KK Women’s and Children’s Hospital (KKH), Dr Shephali Tagore leads in high-risk obstetrics and operative obstetrics, and implements risk reduction strategies towards safer clinical care.

Dr Tagore is also Director of the Obstetrics & Gynaecology International Medical Programme at KKH, and is actively involved in teaching, training and research activities. She has a passion for organising overseas training in obstetrics emergencies within Southeast Asia, and leads teams in teaching simple and safe obstetrics practices to improve perinatal outcomes.

References

1. https://www.cdc.gov/flu/resource-center/freeresources/print/print-pregnant.htm#Vaccination
2. https://www.cdc.gov/vaccines/vpd/pertussis/index.html