1. Influenza (Flu) vaccine
Benefits:
Flu is more likely to cause severe illness (including lung infection) in pregnant women (especially those who are overweight) than in non-pregnant women. Viral influenza vaccination was associated with 50% reduction in confirmed influenza among women and their babies. There was, however, no clear difference between vaccinated and non-vaccinated women in miscarriage, premature labour, stillbirth, admission to hospital for infection for baby or mother.
Risks:
Common side effects include pain and redness, swelling, headache, fever, nausea, muscle aches, fainting.
Rare side effects includes generalized weakness or tingling sensations over the limbs and upper body. Studies have shown a risk of 1-2 of such cases per million people vaccinated.
Schedule:
It is recommended by authorities in many developed countries. This involves one dose of inactivated vaccine any time in pregnancy (consider doing so after 12 weeks). But it is not recommended if you have a history of nerve disorders and probably not a good idea during periods of active Zika transmission as the side-effects of the flu vaccine may mask the symptoms of Zika infection in the mother.
2. Pertussis vaccine
Benefits:
Protects the newborn baby between 0-6 months against whooping cough (pertussis) and tetanus. There has been a surge in whooping cough infections in newborn babies in recent years, and may result in admission to intensive care units in some of them. The immunity you get from the vaccine will pass to your baby through the placenta and provide protection for them until they are old enough to be vaccinated against whooping cough at 6 months old. Currently there isn't a single vaccine against whooping cough alone, so we use a combined vaccine (Tdap).
Risks:
Minor side effects include pain and redness, swelling, headache, tiredness, nausea and vomiting, fever, sore joints, body aches.
Rare side effects include rash, swollen glands, severe allergic reaction estimated in 1:1,000,000 and will happen within a few minutes to a few hours after vaccination, and difficulty moving arm after vaccination.
Schedule:
It is recommended by authorities in many developed countries to be given at 16-32 weeks regardless of prior status. The pertussis-only vaccine is sufficient for this purpose.
For patients going to deliver in countries where neonatal tetanus is still endemic (e.g. India), tetanus toxoid vaccinations for all pregnant women is recommended. The Tdap vaccine (which covers for tetanus, diphtheria and pertussis) replaces the need for an additional tetanus toxoid in such patients. This is not necessary in many developed countries e.g. Singapore as neonatal tetanus is no longer seen.
Maternal Respiratory Syncytial Virus (RSV) vaccination
Recently, Pfizer has come out with a maternal RSV vaccine that has been licensed for use in pregnancy by Health Science Authority (HSA).
I have been asked by my patients about my views on this vaccine. Let me summarize the 2 studies that form my views about this RSV vaccine.
GSK had initially planned for a trial involving 10,000 pregnant women with its RSV vaccine given at 24 to 34 weeks but prematurely terminated their study when the number of participants reach 5,328 because of some adverse safety signals (see https://pubmed.ncbi.nlm.nih.gov/38477988/). Whilst the vaccine reduced the risk of severe RSV lung infection in infants < 6 months by 69%, the rates of preterm births and neonatal deaths were higher in the vaccinated group compared to the non-vaccinated group (preterm births 6.8% vs 4.9%, and neonatal deaths 0.4% vs 0.2%).
Pfizer's study, on the other hand, involved 7,358 pregnant women with its RSV vaccine given 24-36 weeks. It reported that the vaccine reduced severe lung infections in infants < 3 months by 81.8% and in infants < 6 months by 69.4%. It reported no safety signals (see https://pubmed.ncbi.nlm.nih.gov/37018474/). However, if you look at the rate of premature delivery in the table attached below), it was higher for the vaccinated group (like the GSK maternal RSV vaccine) by about 1% (5.7% vs 4.7%) though it was not statistically significant.
The Pfizer RSV vaccine is now approved for use in US and Singapore for pregnant women at 32-36 weeks gestation. This was modified from the initial study's protocol of 24-36 weeks, probably in response to its possible associated risk of preterm birth. An observational study of the vaccine use between 32-36 weeks in 1,026 pregnant women showed did not show an increased risk of preterm birth (5.9% vs 6.7% amongst those who did not take the vaccine' see https://pubmed.ncbi.nlm.nih.gov/38976271/).
I would prefer the publication of real life data involving much higher numbers using this new protocol, and would support the use of this vaccine when this new data proves that it is indeed safe for the babies.
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