Pfizer's Coronavirus vaccine - a closer look

A major milestone for Pfizer

On 9 November 2020, Pfizer announced that its vaccine candidate, developed in collaboration with BioNTech, was more than 90 per cent effective in preventing COVID-19 in participants without evidence of prior SARS-CoV-2 infection in the first interim efficacy analysis.

After discussion with the US Food and Drug Administration (FDA), Pfizer and BioNTech elected to drop the 32-case interim analysis point and conduct the first interim analysis at a minimum of 62 cases. Upon the conclusion of those discussions, the evaluable case count reached 94 and the Independent Data Monitoring Committee (DMC) performed its first analysis on all cases. The case split between vaccinated individuals (9) and those who received the placebo (85) indicates a vaccine efficacy rate above 90%, at 7 days after the second dose.

Dr Anthony Fauci, the US Government’s top infectious diseases expert, said that Pfizer’s interim results were “just extraordinary”.

Pfizer’s result is being praised worldwide, however, it is worth noting that there are some criticisms and concerns relating to Pfizer’s announcement.

One common criticism is that Pfizer’s announcement is based on interim results (at 94 positive COVID-19 cases after seven days post administering the second dose). The reason it is interim is that Pfizer’s clinical trial will continue through to final analysis at 164 confirmed COVID-19 cases in order to collect further data and characterize the vaccine candidate’s performance against other study endpoints. Whilst this is a valid point, performing interim analysis is not uncommon in drug and vaccine development. 

Another criticism is that the announcement was made before these results have been peer-reviewed, which would validate the claims. However, publicly listed companies are obliged to disclose market-sensitive information as soon as they become aware of it and this interim analysis result is clearly highly market sensitive.

Whilst Pfizer has adequately addressed these issues in its announcement, explicitly stating that percentage efficacy may change as further data becomes available, media reporting is not giving the full picture – articles either highlight only the positive news, or focus too heavily on criticisms. Pfizer, with a market cap of USD $218 billion, has much to lose if its media release is found to be less than truthful or inaccurate. Also, Pfizer has little to gain in claiming such an extraordinary result, considering that the FDA announced that it would issue an Emergency Use Authorisation (EUA) for a vaccine that shows at least 50% efficacy. 

Pfizer plans to apply for the EUA once it achieves the required safety milestone, expected in the third week of November. 

There is, however, a legitimate logistical issue with the Pfizer vaccine, which will need to be addressed. Given that it is an mRNA vaccine and must be frozen at below -70°C, there is a concern over the feasibility of transporting the vaccine from its overseas manufacturing site to Australia and then domestically, as Australia does not yet have the technology required for storage. The Australian Government, who has agreed to purchase 10 million doses of the vaccine (enough for 5 million individuals), is working with local providers to solve this logistical issue. 

Pfizer’s announcement is especially significant because it potentially validates the mRNA approach to the COVID-19 vaccine and flags that other vaccine candidates employing the same approach (e.g. Moderna Inc.’s) could be similarly successful.