According to several different studies that have been published recently, Moderna’s mRNA vaccine is the most effective — but experts still don’t entirely understand why.
To be clear, both Pfizer and Moderna’s vaccines are safe and effective at protecting against COVID. “It’s not appropriate for people who took Pfizer to be freaking out that they got an inferior vaccine,” Dr. John Moore, a virologist at Weill Cornell Medicine, told the New York Times. But while the difference is a minor one, it does seem to exist.
When Pfizer was first released to the public, it had a 91 per cent change of preventing hospitalization. Over the last few months, that number has fallen to 77 per cent, according to research from the Centers for Disease Control and Prevention (CDC) published Friday.
Moderna, meanwhile, was found to be 93 per cent effective against hospitalization. That number has not changed.
To be fair, there are some external factors working against Pfizer. The New York Times points out that Pfizer’s vaccine was released to seniors before Moderna’s, for instance — it’s normal for immunity to wear off faster in older adults, which may skew the results. But given how many studies found a decline, it’s worth noticing. The CDC’s findings line up with other studies, including one from the Mayo Clinic and one from Qatar. And Ontario study and a Belgian study both found that people who had received the Pfizer vaccine had fewer antibodies than people who received Moderna’s.
There are a number of reasons Moderna’s vaccine might be more effective than Pfizer’s, epidemiologist Dr. Katelyn Jetelina wrote in Slate. Moderna’s higher RNA dosage than Pfizer could explain why the immune response it provokes is stronger, or lasts longer. But at this point it really isn’t clear. It’s even possible that Moderna’s effectiveness could start to decline, too, she wrote.