AstraZeneca's coronavirus vaccine is simple, inexpensive to manufacture and appears to be effective

In a call with reporters Monday morning, the Oxford scientists said they were still trying to understand why the vaccine was more effective with a lower first dose. The first dose is designed to boost the immune system while the second is designed to boost the response.

While the total data included more than 23,000 participants, fewer than 2,800 received the smaller first dose – a much smaller sample size than the Pfizer and Moderna studies. Almost 9,000 participants received the larger first dose.

Dr. Saad B. Omer, director of the Yale Institute for Global Health, pointed to several possible explanations as to why the dosage regimens produced different results. There could be significant differences between the two groups, such as: B. The age of the participants or their previous exposure to similar viruses that influenced their response.

The design of the vaccine could also play a role: the full dose could give participants immunity to the delivery vehicle and dampen their subsequent immune response. The sample size may also play a role. Fewer participants received the smaller first dose, making their results less statistically meaningful.

Dr. Omer cautioned against drawing definitive conclusions until more details were available. "I would withhold my judgment until we specifically look at more data," he said.

Pam Cheng, executive vice president at AstraZeneca, told reporters on Monday that the company should have four million cans available in the UK by the end of the year if it received regulatory approval. At least 300 million doses of the finished vaccine are expected to be distributed worldwide by the end of March.

Even without delays, however, the vaccine is still a long way from being widely available. Regulators must evaluate the study data and decide whether to approve the vaccine. AstraZeneca needs to ramp up production and work with government officials to introduce cans. And in the first weeks and months after the vaccine is approved, it is expected to be available only to the highest priority groups, likely health workers first, followed by other vulnerable groups.