Pfizer’s new RSV vaccine given to pregnant women to protect their babies shows major promise


Pfizer has announced its experimental RSV vaccine is highly effective — giving a glimmer of hope for parents and doctors.

The pharmaceutical giant announced its shot can reduce the risk of hospitalization among infants up to six months of age infected with the seasonal virus.

If approved, it would be the first vaccine for RSV, which kills between 100 and 500 children under five and hospitalizes about 58,000 each year.

That could prove a lifeline for hospitals which are currently overwhelmed with unseasonably high cases of the virus – which has been blamed on lockdowns suppressing children’s immunity.

The vaccine is administered to pregnant women during the late second to third trimester of their pregnancy. Vaccination during pregnancy allows the antibodies to travel into the placenta, conferring protection to the fetus. 

Pfizer’s trial included 7,400 pregnant women in 18 countries who either received a dose of the experimental vaccine or a placebo.

Pfizer expects to finalize its petition for approval from the Food and Drug Administration by the end of 2022, potentially setting up a federal go-ahead before the next respiratory infection season kicks off. 

The above graph shows the number of positive tests for RSV viruses by date in the United States. It reveals they have now reached their highest levels since 2020, before the pandemic began. Data is from the Centers for Disease Control and Prevention

The immune power of the vaccine when administered to moms-to-be is conferred to babies in utero, which provides them with crucial protection from the virus in their first 90 days of life.

The immune power of the vaccine when administered to moms-to-be is conferred to babies in utero, which provides them with crucial protection from the virus in their first 90 days of life.

Administering the vaccine to expectant mothers was shown to be nearly 82 per cent effective at preventing severe illness caused by RSV in infants during their first 90 days of life. 

At six months, the vaccine was still 69 per cent effective. 

Cases were considered ‘severe’ if the babies infected were breathing very rapidly, over 70 breaths per minute.

RSV cases were also considered severe if the patient’s blood oxygen levels fell below 93 per cent, if they required high-flow supplemental oxygen, if they were admitted to the ICU, or if they lost consciousness.

Severe infections may cause pneumonia and bronchiolitis, an inflammation of the small airways in the lung.

Worldwide, RSV kills about 100,000 children a year, mostly in poor countries. Yet, there is no vaccine for the respiratory condition.

Dr Eric Simões, a pediatric infectious diseases expert at the University of Colorado School of Medicine and Children’s Hospital Colorado celebrated the maternal vaccine, saying it could substantially reduce the number of RSV cases currently in hospitals.

‘And, if approved by regulatory authorities, will likely have a significant impact on disease in the U.S. and globally,’ Dr Simões said. 

Professor Jonathan Ball, Professor of Molecular Virology, University of Nottingham in the UK said that past failures to develop a viable RSV vaccine makes Pfizer’s news all the more exciting

‘The news from Pfizer that their early clinical trial data suggests good protection against lung infection following vaccination of pregnant mothers (who will pass on the immunity to their new born children) is great news,’ Prof Ball said. 

WHAT IS RSV? 

Respiratory syncytial virus (RSV) is a very common virus that almost all children become infected with by the age of two.

In older children and adults, RSV can trigger colds and coughs, but it can cause bronchiolitis in young children.

The virus is spread when an infected person coughs or sneezes. It can survive on a surface for up to 24 hours. 

Children remain infectious for up to three weeks, even after their symptoms have passed.

RSV accounts for 450,000 GP appointments, 29,000 hospitalisations and 83 deaths per year among children in the UK. 

In the US, it leads to around 58,000 hospitalisations and 100 to 500 deaths among children aged younger than five.

Pfizer is expected to be the first company to get its shot across the finish line, but  the exact timeline for approval is unclear

Pfizer CEO Albert Bourla told investors Tuesday that he expects the vaccine could be available by late 2023 or early 2024.

Children’s hospitals across the US are stretched thin amid a deluge of sick children whose immune systems have been shielded from many common pathogens over the past two years.

Two years without RSV circulating widely means millions of young children will encounter the pathogen for the first time in their lives this year.

A combination of social distancing, masking, and remote learning that was adopted to protect people from Covid-19 effectively halted infectious viruses like RSV in their tracks.

Now that those mitigation measures have largely been dispensed with, RSV has made a roaring comeback.

This year’s RSV season kicked off about two months ahead of schedule. The wave of sick children taking over pediatric units in major hospitals has forced workers there to adjust who provides care and where.

At Johns Hopkins Children’s Center in Baltimore, for instance, floor nurses will be deployed to pediatric patient units to deal with the influx. 

Doctors who normally treat adults will begin caring for children in a reversal from early pandemic protocol when pediatricians were enlisted to treat the inundation of adult Covid-19 patients.

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