Five things to know about Pfizer's COVID-19 vaccine that's 90% effective, including India availability

US drug major Pfizer and German biotech firm BioNTech have pleasantly surprised the world on November 9 by announcing that their potential COVID-19 vaccine was found to be more than 90 percent effective in tackling the novel coronavirus.

The companies said the first interim efficacy analysis suggested that their COVID-19 vaccine candidate was found to be more than 90 percent effective in preventing COVID-19 infection in participants who had no prior history of SARS-CoV-2 infection.

The announcement of early positive results from a late-stage clinical trial puts Pfizer-BioNTech ahead of other vaccine makers.

Pfizer and BioNTech's COVID vaccine candidate is based on genetic material or mRNA that instructs human cells to make SARS-CoV2 antigen, eliciting an immune response.

What data suggests about the vaccine?

Pfizer said its analysis evaluated 94 confirmed cases of COVID-19 in clinical trial participants. The cases split between vaccinated individuals and those who received a placebo. Pfizer said the vaccine data indicated an efficacy rate above 90 percent, just 7 days after the second dose. Pfizer didn't disclose how many of the confirmed cases have received the vaccine and how many got the placebo.

According to Pfizer, protection is achieved 28 days after the initiation of the vaccination, which consists of a two-dose schedule. The interim efficacy analysis was conducted on November 8 by an external, independent Data Monitoring Committee (DMC). The DMC has not reported any serious safety concerns and recommends that the study should continue to collect additional safety and efficacy data as planned. The data will be discussed with regulatory authorities worldwide.

Pfizer phase-3 study enrolled 43,538 participants, with 42 percent having diverse backgrounds, and no serious safety concerns have been observed; Safety and additional efficacy data continues to be collected.

What is an interim review, how is it done?

As per Pfizer's protocol, which was made public in September, the first interim analysis was to occur after 32 trial participants tested positive. The 32 participants are split between those who got the vaccine shot and those who received the placebo. If fewer than six participants test positive in the vaccine group, the vaccine is considered effective. For the final analysis, of 164 cases, it will need to hit 50 percent efficacy to be deemed a success by the US Food and Drug Administration (USFDA). In the case of Pfizer, after discussions with the USFDA, the companies have elected to drop the 32-case interim analysis and conduct the first interim analysis at a minimum of 62 cases. Upon the conclusion of those discussions, the evaluable case count reached 94. In essence, Pfizer's first interim review was done on a much bigger sample, making the results all the more interesting.

What next for Pfizer?

Pfizer said it plans to ask the US FDA for emergency authorisation of the two-dose vaccine later this month, after it has collected the recommended two-month safety data. Meanwhile, the clinical trial will continue through to final analysis at 164 confirmed cases in order to collect further data and characterise the vaccine candidate’s performance against other study endpoints. As the study continues, Pfizer said the final vaccine efficacy percentage may vary.

How much can Pfizer produce, will it be available in India?

Based on current projections, Pfizer said it expects to globally produce up to 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021. The New York Times reported that by the end of the year, Pfizer will have manufactured enough doses to immunise 15 to 20 million people. Pfizer hasn’t yet announced its plans to make this vaccine available in India. The vaccine also requires specialised cold storage; it has to be stored at -94 degrees Fahrenheit, which could be a potential bottleneck in India for mass rollout, pushing the cost of the vaccine. The high cost of the vaccine may become a deterrent to mass distribution in India, but could possibly be available in the private label market for those who can afford it.

The US government has signed a $1.95 billion deal with Pfizer to buy 100 million doses of the vaccine if it receives regulatory approval. The deal indicates a price of $19.50 per dose, or $39 for a two-dose regimen. While the Indian government hasn't yet publicly announced the price at which it procures the vaccine, Serum Institute of India has offered the AstraZeneca vaccine at a maximum price of $3 per dose or Rs 250. ​

What experts say

Experts are waiting to see more data from Pfizer and BioNTech, and asked people to be cautiously optimistic, as this is still early data.

"This is good but we can comment properly when more details are available," said Dr Gagandeep Kang, India's leading expert on vaccines and Professor at the Department of Gastrointestinal Sciences at Christian Medical College, Vellore.