After the news that Pfizer/BioNTech vaccine demonstrated progress today, frustrated mask wearers all over the world rejoiced at the headline. The pandemic is over, or so they thought. However, more meticulous Covidologists scrutinized the carefully worded press release for actual information.
What they found was some cause for optimism and lots of uncertainty.
The data from the study was compiled from an interim analysis. The study is not over, but the signal from the trial was strong enough that the companies decided to release the early results with the understanding that more detailed results will be available at a later time. The next set of results will include safety data after two months post-vaccine for the participants which will occur in the third week of November. Sufficient safety data at that time will position the company for applying for Emergency Use Authorization around early December potentially.
The actual release did contain some impressive data. The study evaluated 94 confirmed cases of Covid-19 among its 43,538 volunteers. In the results, the two-part vaccine was found to prevent 90% of the Covid-19 cases in the vaccine-treated population. This finding easily cleared the 50% hurdle that the study was trying to achieve. The study also did not reveal any glaring early safety concerns.
But there are many reasons to mute the optimism as has been pointed out by multiple reviewers.
In a field where billions of healthy patients will receive this vaccine, safety is just as important as efficacy. In this area, the Pfizer/BioNTech data was very thin. Additionally, the companies plan on only releasing two-month safety data whereas other vaccine trials have had the benefits of years of follow-up. Moreover, this vaccine along with Moderna vaccine are using a technology that has never been used for a vaccine before. No one knows the risk of whether the genetic manipulation needed to construct the vaccine can create unforeseen issues. One of the major risks described with vaccines is a frightening entity called Guillain-Barre syndrome which can result in major paralysis. This side effect occurred in the past at a rate of about 2 per million cases. A small sample size of forty or so thousand may miss many rare side effects that would show up in larger populations.
Durability is another issue. Previous studies have already shown that antibody titers decrease after these Covid-19 vaccines. In this study with 2 month follow-up, the duration of the effect past multiple months is completely unclear. Longer documentation of disease protection to understand whether the vaccine is effective after initial administration and whether boosters are needed.
The delivery of the vaccines will be a major issue. The Pfizer/BioNTech vaccine will be extremely challenging. Most importantly, this particular vaccine and that of the other mRNA vaccines which includes the Moderna vaccine require storage at -4 degrees Fahrenheit. This fact greatly limits the ability to transport the vaccines across the country and the globe. Additionally, this vaccine has the most discomfort to patients in that it can cause a local reaction and/or fevers after each injection. Another logistically challenging issue is that it requires two separate injections weeks apart to gain the effect. If someone has a bad initial reaction, they may be reluctant to receive the second shot. Also, even though the companies plan to give out 50 million vaccines this year, they have not clarified their manufacturing timeline or whether these doses are currently available.
Several other vital areas of data were missing. The press release did not document whether the virus was effective in elderly or vulnerable populations, the very individuals who are dying in this pandemic. It did not say whether it prevented serious illnesses. Most importantly, the data did not mention whether the vaccine prevented infectivity or just symptoms. Currently, people are fearful of visiting elderly relatives due to fear of infecting them. This vaccine may not provide sterilizing immunity and thus still allow the individual to give others Covid-19. The vaccine is not that useful if it prevented mild or asymptomatic cases and did not mitigate the spread of serious disease. Also, without this type of immunity masking and distancing will still be necessary until a near-complete proportion of the population have been vaccinated.
The first major Phase 3 vaccine results have been given in top-line form and the next phase of the pandemic is poised to begin. Let us hope that more of these questions can be answered when this next phase is underway.