(Reuters) – The second dose of Pfizer Inc.’s COVID-19 vaccine could be delayed to cover all priority groups, as the former is highly protective, two Canadian-based researchers said in a letter published in New England Journal of Medicine.
The vaccine was 92.6% effective after the first dose, Danuta Skowronski and Gaston De Serres said, based on an analysis of documents submitted by the pharmacist to the U.S. Food and Drug Administration (FDA).
These results were similar to the effectiveness of the first 92.1% dose reported for Moderna Inc.’s mRNA-1273 vaccine, according to Wednesday’s letter.
In its response, Pfizer said alternative vaccine dosing regimens had not yet been evaluated and that the decision rested with health authorities.
Some countries, with few supplies, are studying dosage patterns or volumes that differ from how vaccines were tested in clinical trials.
There are differences on the merits of these strategies, some arguing that the urgency of the pandemic requires flexibility, while others oppose abandoning data-driven approaches for convenience.
Skowronski and De Serres warned that there may be uncertainty about the duration of protection with a single dose, but said administering the second dose a month after the first provided “little added benefit in the short term.”
Skowronski works at the Center for Disease Control in British Columbia, while De Serres is from the National Institute of Saint Publique in Quebec.
In Britain, authorities have said the data supported their decision to move to a 12-week dosing schedule for Pfizer’s COVID vaccine. Both Pfizer and its partner BioNTech have warned that they had no evidence to prove it.
Pfizer vaccine is allowed 21 days apart.
The U.S. FDA and European drug agency have been stuck for the interval tested in the trials.
Report by Shubham Kalia and Ann Maria Shibu in Bengaluru; Edited by Vinay Dwivedi and Sriraj Kalluvila