US approves Pfizer’s maternal RSV vaccine to protect infants

Toward preventing lower respiratory tract infection and severe disease in infants, the American Food and Drug Administration on Monday (FDA) approved the Respiratory Syncytial Virus (RSV) vaccine for use in women during the middle of the third trimester of pregnancy.

The approval allows the vaccine to be given to women 32 to 36 weeks into pregnancy to protect the infants until they are six months old.

The shot becomes the second RSV vaccine, and third new intervention against the disease this year.

In May, the FDA approved the Abrysvo vaccine for preventing RSV in people 60 years and older.

The same vaccine is now approved for pregnant people in their third trimester. And in July, the agency approved nirsevimab, an antibody-based injection that protects babies immediately after birth from RSV.

In a statement published on its website, the FDA said Abrysvo is administered as a single-dose injection into the muscle.

The director of the FDA’s Centre for Biologics Evaluation and Research, Peter Marks, said RSV is a common cause of illness in children, and that infants are among those at the highest risk for severe disease, which can lead to hospitalisation.

Mr Marks said this approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease.

About RSV

RSV is a highly contagious virus that causes respiratory infections in individuals of all age groups.

It is the most frequent cause of lower respiratory tract illness in infants worldwide. In most parts of the U.S., RSV circulation is seasonal, typically starting during the fall and peaking in the winter.

The virus is especially common in children, and most individuals can be expected to be infected with RSV by the time they reach two years of age.

“While RSV most often causes cold-like symptoms in infants and young children, it can also lead to serious LRTD such as pneumonia and bronchiolitis (swelling of the small airway passages in the lungs),” he said.

“In infants and children, the risk of RSV-associated LRTD is highest during the first year of life.”

The new interventions have been a long time coming in RSV treatment, which in the U.S. sends 58,000 to 80,000 children under age five to the hospital each year and kills 100 to 300 annually.

Vaccine

Pfizer, which makes Abrysvo for both older people and now those who are pregnant, has been developing the shot since the 2010s after scientists at the National Institutes of Health discovered just the right form of RSV to capture in the vaccine and present to the immune system. 

In a study reviewed by the FDA involving pregnant women in 18 countries, the vaccine was 81.8 per cent effective in preventing severe respiratory illnesses needing medical attention in babies in the first 90 days after birth.

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The FDA said the most common side effects in pregnant women were fatigue, headache, pain at the injection site, muscle pain, nausea, joint pain, and diarrhoea.

“The safety of Abrysvo was evaluated in two studies. In one study, approximately 3,600 pregnant individuals received a single dose of Abrysvo and approximately 3,600 pregnant individuals received a placebo,” it said.

“In the second study, approximately 100 pregnant individuals received Abrysvo and approximately 100 pregnant individuals received placebo.”

It said although not commonly reported, a dangerous hypertensive disorder, known as pre-eclampsia, occurred in 1.8 per cent of pregnant individuals who received Abrysvo compared to 1.4 per cent of pregnant individuals who received a placebo.

It noted that in the safety studies, low birth weight and jaundice in infants occurred at a higher rate in the pregnant Abrysvo recipients compared to pregnant placebo recipients.