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AstraZeneca Faces Hurdles to Regulatory Approval of COVID19 Vaccine

AstraZeneca
 the staff of the Ridgewood blog
Ridgewood NJ, previously reported on the Ridgewood blog that AstraZeneca issued a press release regarding preliminary results from the Phase 3 clinical trials of its candidate SARS-CoV-2 vaccine, developed in collaboration with Oxford University (UK). According to Johns Hopkins Center for Health Security ,the press release indicates that the vaccine demonstrated 90% efficacy when administered as an initial half-dose followed by a full dose a month later. Interestingly, however, the vaccine was 62% efficacious in participants who received 2 full doses over the same period of time, resulting in an overall efficacy of 70%. No serious adverse events were identified in the trials. In total, the Phase 3 portion of the trials included more than 11,000 participants, and the researchers identified 131 COVID-19 cases. As has been the case throughout the pandemic, the data published via press release have not yet been peer reviewed, although the researchers reportedly intend to publish the full data in the near future.

The increased efficacy among participants who received the initial half-dose has sparked interest among experts. This analysis was based on only 2,741 participants who appear to have received the smaller dose unintentionally, according to a statement by AstraZeneca. The mechanism by which the smaller first dose resulted in higher efficacy is unclear, but representatives from AstraZeneca indicate that this dosing regimen will be investigated further to better characterize its effects. One theory is that the smaller initial dose is not enough to stimulate a full immune response, which could reduce the likelihood that the immune system would suppress the second “booster” dose. At 70% efficacy, the AstraZeneca vaccine could face challenges in terms of regulatory approval, as there are already 2 vaccines with reported efficacy in excess of 90%; however, if the half-dose regimen is, in fact, more efficacious, it could provide a third option.
The AstraZeneca vaccine can be stored at normal refrigeration temperatures for up to 6 months. AstraZeneca has already committed to providing more doses globally than any other manufacturer by a factor of 2 over the nearest manufacturer (Novavax)—including for low-and-middle-income countries and the WHO COVAX Facility.
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