The US Food and Drug Administration (FDA) in 2023 approved 2 vaccines for use in adults aged 60 years and older to reduce the risk of serious respiratory syncytial virus (RSV) disease: GSK’s Arexvy and Pfizer-BionTech's Abrysvo. A savvy patient may ask which one you would recommend for them. Let's explore the differences between the 2 that might help guide your decision.
The side effect profile for both vaccines is similar— it's the usual suspects seen with all IM vaccines ie, sore arms, fever in some, malaise in some. Both products, however, had a non-significant increase in cases of Guillain-Barré syndrome in the vaccine arms of the trials as compared to the placebo arms. The FDA is requiring post marketing surveillance to see if this is a real signal or a statistical anomaly. There is no advantage to either vaccine here.
Efficacy was good for both vaccines in the registration clinical trials but since there has been no head-to-head study, one cannot look at the reported numbers as “proving” that one is better than the other.
As to differences, the patient populations differed between the studies. Pfizer's cohort was younger and had fewer comorbid conditions compared to those in the GSK phase 3 trials. The studies had slightly different end point goals as well. GSK reported overall vaccine efficacy (VE) of 83%, but in study participants with at least one comorbidity VE was 95%. Pfizer reported VE of 86%. The CDC was happy with both studies and does not recommend one over the other. Again, no advantage of one vaccine over the other.
If you live in an area where vaccine hesitancy or skepticism is high, however, then one vaccine may offer a slight advantage.