(WXYZ) — Abrysvo is made by Pfizer, and it’s a single shot given to moms-to-be between 32 and 36 weeks of pregnancy. It works through a process called maternal immunization. This means that when pregnant mothers get the shot, they create antibodies to fight RSV. These antibodies are then passed to the growing baby through the placenta.
Now, the protection from the vaccine lasts about six months for newborns. In a clinical trial, the vaccine reduced the chance of severe RSV disease by about 82% during the first three months after birth. However, by six months of age, the effectiveness decreased to around 69%.
As for how safe and effective Abrysvo is, Pfizer needs to conduct ongoing studies to monitor the risk of preeclampsia and preterm birth. Preeclampsia is a dangerously high blood pressure disorder that can happen during pregnancy. In clinical trials, around 1.8% of pregnant moms who received Abrysvo had preeclampsia, while about 1.4% of those who were given a placebo developed it.
Regarding pre-term births - that's when babies are born earlier than expected - there was a slightly higher number in mothers that received the vaccine compared to the mothers that were given a placebo. It was 5.7% compared to 4.7%. The FDA saw this difference as "a numerical imbalance." The prescribing information given to doctors will have a warning to be sure the vaccine is only given between the 32nd and 36th weeks of pregnancy.
Abrysvo is the first vaccine to prevent RSV in newborns, and it’s the second treatment to receive FDA approval. An antibody called Nirsevimab was recently approved by the FDA for babies and toddlers. In clinical trials, it reduced the chance of babies needing medical care by about 70%. It was also 78% effective at preventing hospitalization.
Furthermore, two other RSV vaccines made by Pfizer and GlaxoSmithKline were also approved. However, these are currently only offered to older adults.
Regarding the availability of Pfizer's vaccine for pregnant mothers, it still needs a recommendation from the CDC. The advisory panel is expected to meet in October. So, Abrysvo could be ready for expectant mothers sometime around Halloween or the beginning of November.
