A new study released by the US Centers for Disease Control and Prevention (CDC) on Friday is the latest to suggest the Moderna Covid vaccine confers better long-term protection against hospitalization than Pfizer.
CDC researchers conducted an analysis of nearly 3,689 adults who were hospitalized with severe Covid from March 11 to August 15, 2021 -- a period that precedes and includes the dominance of the Delta variant.
Overall, 12.9 percent were fully vaccinated with the Moderna vaccine, 20.0 percent were vaccinated with Pfizer-BioNTech, and 3.1 percent were vaccinated with Johnson & Johnson.
Over the entire period, the Moderna vaccine was 93 percent effective against hospitalization, Pfizer was 88 percent effective, and J&J was 68 percent effective.
The loss of efficacy against hospitalization for Pfizer was particularly pronounced: it fell from 91 percent in 14-120 days after vaccination to 77 percent more than 120 days after vaccination.
By contrast, Moderna fell from 93 percent to 92 percent when comparing the same two periods.
The study also included a separate analysis of the levels of different types of antibodies provoked by the vaccines, taken from 100 volunteers.
The Moderna vaccine elicited higher levels of antibodies compared to Pfizer and J&J for a key part of the virus' spike protein, which it uses to invade cells.
There is accumulating research suggesting the Moderna vaccine's superiority over the Pfizer vaccine, including a previous CDC studies released last week.
The reasons aren't fully clear, but it could be because the dosage levels are higher -- 100 micrograms against 30.
It could also be tied to the dosing interval, with the Pfizer shots given three weeks apart versus Moderna, which are given four weeks apart.
The Food and Drug Administration was holding a meeting of leading independent experts on Friday to weigh the question of giving third doses of Pfizer to the general population, not just immune compromised people.