The interim results from an ongoing phase 3 trial show their vaccine candidate presents a 90% efficacy preventing symptomatic COVID-19 infection. But it’s hard to imagine having mass distribution in countries with severe energy deficits.
By Caracas Chronicle – Juan Carlos Gabaldón
Nov 10, 2020
“Today’s a great day for science and humanity. The first set of results from our phase 3 COVID-19 vaccine trial provides the initial evidence of our vaccine’s ability to prevent COVID-19,” said Dr. Albert Bourla, CEO of Pfizer, at a press conference yesterday. The vaccine has already proven to cause only mild adverse effects and a strong immune response, and it’s being tested in a wide range of ages, including teenagers and the elderly.
As we have previously explained, unlike phase 1 and 2 trials which mostly focus on safety data and immunogenicity, phase 3 trials actually check how effective an intervention is to treat (or in this case, prevent) a disease. In this stage, researchers recruit a large group of people (over 43,000 people in six countries, including Argentina and Brazil, for this trial), some of which receive the vaccine, and some of which receive a placebo. Then, they evaluate – among many other things – if there are significant differences in the proportions of people getting the disease between both groups. If the vaccine is effective, you would expect considerably less vaccinated participants to get ill.
And that’s just what Pfizer’s preliminary results show. They’re also the first company to present preliminary results of a phase 3 trial, which began in late July.
Pfizer and BioNTech’s vaccine candidate is based on state-of-the-art RNA technology, similar to the one developed by American company, Moderna. RNA is the blueprint to build proteins. These vaccines include viral RNA, which our cells use to produce a SARS-Cov-2 protein; this protein is then recognized as foreign by the immune system, triggering a strong response that protects you from the disease.
BNT162b2 is made up of two doses administered 21 days apart. Researchers found that the incidence of new COVID-19 cases in previously unexposed, vaccinated participants within the first seven days following the second dose was 90% lower than in the unvaccinated group.
It’s important to point out that the endpoint evaluated by researchers was the number of symptomatic COVID-19 cases, which is not the same as the number of SARS-Cov-2 infections, since we know that many cases are asymptomatic. This means that despite effectively preventing the development of clinical disease, we still don’t know if the vaccine prevents infection, and therefore transmission of the virus. As long as we’re unable to prevent transmission, social distancing measures will need to remain in place, at least until the most vulnerable groups are protected from developing severe disease.
For this reason, it’s safe to assume that these groups (healthcare workers, the elderly, patients with pre-existing chronic conditions) would receive the vaccine first.
It’s also hard to imagine Venezuela’s wrecked hospitals equipped with the freezers needed to store the Pfizer vaccine.
These results haven’t been published yet, nor peer-reviewed. They were announced in a press conference, following the initial analysis of a Data Monitoring Committee (DMC); these committees are independent from the main researchers, and regularly monitor the data collected at different moments of the trials, to make sure the participants’ safety is guaranteed and the study is worth continuing. Nonetheless, they don’t substitute the rigurosity of a peer review and avoiding science by press conference is a general rule of thumb. Patients are expected to be monitored at least until December 2022, but we’ll have definitive results way earlier.
Another important limitation is that RNA is a remarkably unstable molecule and must be stored at extremely low temperatures to prevent degradation. This means that Pfizer’s vaccine must be kept at -80°C until right before administration, a logistical challenge particularly in low and middle-income countries, where sustaining such a complex cold chain is very complicated.
It’s not yet clear how these countries will afford the vaccine, either. Multilateral organizations and global health partnerships will likely prove to be vital, but even then, the problem of scaling up production will remain. Pfizer said it’ll only be able to produce about 50 million doses of the vaccine this year (to protect 25 million people). It expects to produce up to 1.3 billion doses during 2021, a truly remarkable number, but still far from the required figures to bring the pandemic to an end.
But these results suggest other vaccines using similar approaches will likely have positive results as well. There are currently eleven vaccine candidates in phase 3 trials. If other companies can manufacture their own vaccines, this could help curb the scaling up issue.
As for Venezuela, it’s just too soon to know when and which vaccine will arrive. Nicolás Maduro’s regime has so far decided to lean on its traditional allies, suggesting Venezuela could collaborate in phase 3 trials of Chinese an Russian vaccine candidates. It’s also hard to imagine Venezuela’s wrecked hospitals equipped with the freezers needed to store the Pfizer vaccine. Considering how increasingly dystopian the country has gotten, and the now common trend of the government surrendering its basic responsibilities to shady private investors, I wouldn’t be too surprised to find this, and other vaccines, somehow imported in small numbers, destined to those who can pay via Zelle.
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