(Reuters) – The second dose of Pfizer Inc’s COVID-19 vaccine could be postponed to cover all priority groups, as the first is highly protective, two Canadian researchers said in a letter published in the 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 the documents submitted by the pharmacist to the US Food and Drug Administration (FDA).
These findings were similar to the effectiveness of the first 92.1% dose reported for Moderna Inc’s mRNA-1273 vaccine, according to the letter here on Wednesday.
In its response, Pfizer said that alternative dosage regimes for the vaccine have not yet been evaluated and that the decision rested with health officials.
Some countries, struggling with a lack of supplies, are seeing patterns or dosage volumes that differ from how vaccines were tested in clinical trials.
There are differences on the merits of such strategies, with some arguing that the urgency of the pandemic requires flexibility, while others are opposed to abandoning data-based approaches for the sake of convenience.
Skowronski and De Serres warned that there may be uncertainty about the duration of protection with a single dose, but said that the administration of the second dose a month after the first provided “little added benefit in the short term”.
Skowronski works at the British Columbia Center for Disease Control, while De Serres is from the Institut National de Santé Publique du Québec
In Britain, officials said the data supported their decision to switch to a 12-week dosing schedule for Pfizer’s COVID vaccine. Both Pfizer and partner BioNTech warned that they had no evidence to prove this.
The Pfizer vaccine is authorized to be administered 21 days apart.
The US FDA and the European Medicines Agency kept the range tested in the tests.
Reporting by Shubham Kalia and Ann Maria Shibu in Bengaluru; Editing by Vinay Dwivedi and Sriraj Kalluvila