An experimental vaccine developed by Pfizer Vaccine and BioNTech has been shown to be effective in preventing Covid-19 infections in phase 3 trials, the two laboratories announced on Monday. For the rest, it’s still a bit hazy. What do we know exactly?
Everything You Need To Know About Pfizer’s Vaccine
The news made noise, hinting at the end of the long tunnel. A vaccine developed jointly by Pfizer (United States) and BioNTech (Germany) would be “90% effective” in preventing Covid-19 infections according to the two laboratories, which are based on the preliminary results of their large-scale trial phase 3 scale still in progress. The two companies concerned even plan to submit an emergency use authorization request to the FDA, the US health agency. Subject to approval, the vaccine could be available before the end of December.
Researchers and experts around the world have naturally welcomed this breakthrough. They call for caution, however, highlighting the lack of detailed data.
How the vaccine works
Named BNT162b2, the vaccine from Pfizer and BioNtech is a formula based on mRNA. Like the one developed by Moderna, this vaccine relies on capsules of fatty nanoparticles to deliver fragments of genetic code in the form of SARS-CoV-2 messenger RNA (or mRNA) into human cells. Concretely, these “pieces of codes” are a genetic extract of the famous peak protein of the virus thanks to which it attaches itself to human cells before initiating an infection.
Once delivered inside human cells, these genetic extracts are “read” by human cells which then produce the protein fragment. This is then used to train the immune system to detect and destroy the virus.
Pfizer and BioNtech have already released data on their vaccine in previous trials. These first results then showed that their solution triggered an immune response. They also found no serious side effects, highlighting some common mild effects such as pain at the injection site, muscle pain, fatigue, fever, and headaches.
The two laboratories also noted that their vaccine seemed to cause higher levels of antibodies against SARS-CoV-2 than those observed in people who have recovered from Covid. In addition, their vaccine is said to have elicited strong T cell responses, which is essential to consider long-term immune protection.
The phase III trial
Pfizer and BioNTech began their Phase III clinical trial on July 27, 2020. A total of 43,538 participants from the United States, Argentina, Brazil, South Africa, Germany, and Turkey were recruited. . All were divided into two groups: one, of 38,955 subjects, received the vaccine as two injections 21 days apart, and the other a placebo.
Patient protection would then have been obtained seven days after the injection of the second dose (ie 28 days after the first). According to Pfizer and BioNTech, this famous “vaccine efficacy rate of more than 90%” was measured by comparing the number of participants infected with the coronavirus in the group that received the vaccine and in that under placebo. Concretely, this first analysis was carried out after 94 participants in the trial contracted the coronavirus. The researchers then determined how many of those infected participants had received the vaccine, and how many had received the placebo.
Although this news is indeed positive, some missing data should lead us to remain cautious. For example, it is not known whether the vaccine is able to prevent severe or fatal cases of Covid-19. In addition, the trial only considered cases with at least one predetermined symptom of the disease and a positive test. Thus, these early trial data do not indicate whether the vaccine could prevent asymptomatic infection. Finally, today it is impossible to know how long this apparent protection could last or if more serious side effects could develop in the medium or long term.
In the meantime, Pfizer and BioNTech are preparing their data for publication in a peer-reviewed scientific journal. They emphasize being able to produce up to 50 million doses of vaccine worldwide in 2020 and up to 1.3 billion doses in 2021.