Researchers Are Starting For Longer Dosing Periods For Pfizer-BioNTech.
Researchers in Canada, Italy, and the United States are promoting an extension of the interval between two doses of Pfizer-BioNTech 2019 vaccine for coronavirus disease (COVID-19) in people previously unfamiliar with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).
The team found that although administration of the second dose after 16 weeks did not significantly improve the humoral response (antibody) in people infected before the first dose, it did enhance that response substantially in people who were not infected. Andres Finzi of the CHUM research center in Montreal, Quebec, and his colleagues say the results will help dispel fears that more prolonged doses could affect the vaccine's effectiveness.
More about extending the vaccination interval
This vaccine targets proteins in the virus that mediate the infection process when it binds to host cells. Therefore, this jump is the main target of antibodies after vaccination or natural infection.
The standard approved vaccination schedule with BNT162b2 consists of two doses at intervals of 3 to 4 weeks. However, in the early stages of vaccine rollout in winter and spring 2021, the lack of vaccine deliveries led some health authorities to extend this interval to maximize the number of people who could be vaccinated.
This strategy is supported by research showing that a single dose provides about 90% protection just two weeks after vaccination. However, the decision has raised concerns about vaccine effectiveness, especially about the SARS-CoV-2 Variants of Concern (VOC) and of Interest (VOI) which have emerged rapidly and spread worldwide.
These variants are more infectious than previously circulating strains and, in some cases, more resistant to neutralizing antibodies produced after vaccination. For example, the spike mutation D614G, which appeared early in the pandemic, is now present in almost all circulating strains, and variant B.1.1.7 (alpha).
More recently, the highly contagious B.1.617.2 (Delta) strain, which appeared in India in spring 2021, has developed into the dominant variety in several countries. Although some vaccines are highly effective in protecting against serious diseases caused by these variants, some have also produced a less effective neutralizing antibody response. However, most of these studies analyzed plasma samples taken from individuals vaccinated with short dosing intervals (3 to 4 weeks).