According to results released by Oxford University in partnership with AstraZeneca, The university's vaccine had tolerable side effects in the short term, including sore arms, tiredness, headaches, muscle pain and chills and results from the first dose demonstrated a satisfactory level of safety. The early-dose safety signal has led some clinicians to conclude that small doses might not be the safest way to use them. The FDA found that not enough evidence were sufficient to conclude unequivocally on the efficacy of the vaccine. Members of the Consultative Committee will meet for a full-day conference on Thursday.
Oxford and AstraZeneca agreed to supply the vaccine for US$2-$3 per dose to consumers. The vaccine consists of a coronavirus protein encoding DNA that is shuttled into cells in a harmless virus. The medication would be cheaper and simpler to manufacture in bulk than Pfizer and Moderna's RNA vaccines. In combination, the expected amount of doses will still not be adequate to vaccinate the planet.
British authorities last week cleared the vaccine and gave the first shots on Tuesday. Around 44,000 people tested the vaccine and half got two real-life doses of it. The FDA analysis found that the effectiveness of the vaccine across subgroups was "uniformly high." This month's Pfizer vaccine would be the first of two regulator-related vaccines. Next week, Moderna, a biotech company focused on the same technology of coronavirus vaccine, is scheduled for discussion.
The FDA asks its committee to decide whether the vaccine will prevent Covid-19 effectively. The research did not determine the effects of vaccination for people who had been previously infected. Pfizer expects to receive nearly half of its global supply by the end of the year. Preliminary findings released last month showed an unexplained increase in vaccine efficacy. Some statisticians have raised concerns that the study pools data from multiple trials.
The study showed that the vaccine was 70 percent effective against symptomatic coronavirus infections when the different dosing regimes were combined. The standard dosing regimen had an efficacy of 62 percent, with two doses of the same strength given a month apart, whereas the regimen with a lower initial dose provided 90 percent efficacy. "The efficacy and the safety are fine" says virologist Stephen Griffin of Leeds University, UK according to an article published in Nature, "Overall, what you can say is that it does work."
Investigators of the study said that the data was collected in compliance with the regulatory guidelines. Researchers have failed to understand how to achieve higher efficacy from a lower initial dose. Nobody over the age of 55 was also included in the low-dose arm of the study, raising concerns that higher efficacy was merely a by-product of excluding the age group that was extremely vulnerable to COVID-19. Earlier vaccine studies showed that immune responses were similar to those of younger study participants in people over 55 years of age.
Another lingering concern is whether the vaccine is capable of combating asymptomatic infections; it may be necessary to shape the trajectory of the pandemic with immunization that might prevent them. The Oxford-AstraZeneca team is the only one of the three leading developers of vaccines who tested participants for asymptomatic infections by taking weekly swabs to decide whether they had the coronavirus but were not sick. The data showed that the low-dose vaccine protocol was approximately 60% effective in reducing asymptomatic infections, but it was unknown if such infections had been substantially reduced by the regular dose.
Asymptomatic infections have some researchers worried, as people who have those infections may inadvertently begin to transmit the virus to other people within the community even though they are vaccinated. Whilst asymptomatic infections are not a direct measure of disease transmission, researchers have looked at these details as an indication of the degree to which vaccines may influence COVID-19 spread.
The two leading RNA vaccines did not collect asymptomatic infection results, but were more than 90 percent effective in preventing COVID-19 symptoms. And even if the Oxford vaccine's effectiveness happens to be lower than that of the other two, it's still likely to be effective, Griffin says. It is important to balance the lower effectiveness against the practicalities of vaccinating anyone who wants it, he adds. "A cost-benefit analysis is going to come down to that," he says.