Pfizer and BioNTech concluded Phase 3 studies of COVID-19 vaccine candidate, BNT162b2, on 18 November, announcing that primary efficacy analysis indicated that it is 95% effective against the coronavirus beginning 28 days after the first dose.
In contrast, the British-Swedish pharma company AstraZeneca, which has long been seen as a frontrunner in the COVID vaccine race, has yet to present its product over confusing clinical trial results. The UK government swiftly jumped at the opportunity to approve BNT162b2 for emergency use following a nod from the country's national medicine regulator. The US Food and Drug Administration (FDA) is only due to discuss the Pfizer-BioNTech vaccine next week, prompting a rebuke from President Donald Trump who chastised the agency for "dragging its feet" about the long-anticipated drug.
Pfizer Given Green Light in UK, Many More to Come
"The Pfizer-BioNTech vaccine has a better safety profile and it does not have pre-existing antibody and cellular immunity against it as in the case of AstraZeneca/Oxford vaccine", says Jin Dongyan, a virologist and professor at the University of Hong Kong. "More vaccines will be approved one after another in the coming months".
The Pfizer-BioNTech drug will be made available across the UK starting next week, according to the government's website. British Secretary of State for Health Matt Hancock specified that initially the UK would get 800,000 doses with a network of 50 hospitals ready to deliver the first shots. However, rolling out the vaccine across the country will be challenging because it needs to be kept at -70C, The Guardian highlighted citing the health secretary. The Pfizer vaccine requires two shots: a booster should be given three weeks after the first injection. The UK has ordered 40 million doses of the drug which will be enough to immunise 20 million Britons.
"The UK government has approved the Pfizer vaccine first, but they are likely to review and approve the vaccines from Moderna and AstraZeneca after they have collected the same amount of patient data", suggests Andrew Hill, senior visiting research fellow from the Department of Pharmacology at the University of Liverpool.
Meanwhile, Russia, which registered the first anti-coronavirus vaccine in the world, Sputnik V, in August 2020, has already begun coronavirus vaccinations and will proceed with a nationwide immunisation campaign next week. In late November, Russia's Sputnik V arrived in Europe: Hungary became the first EU member state to receive samples of the Russian-made drug.
A Lot of Time Needed to Clear Up Unknown Issues About COVID Vaccines
Not everyone infected by SARS-CoV-2 develops the disease, some remain asymptomatic but nevertheless transmit the virus to others. Vaccination stimulates the human body's protective responses which stop the infection from spreading and causing the disease. The question, however, is whether a vaccine can prevent both the disease and the transmission of the virus.
"We do not know for [an] absolute certainty that people who are vaccinated, then exposed to the virus and do not get clinical symptoms definitely cannot spread the disease – it is impossible in a usual trial to measure this spread to other people who are not in the trial", explains Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine.
All of the knowledge scientists have about virus transmission makes it very likely that asymptomatic as well as symptomatic infection is reduced by a vaccine that shows good efficacy, according to the academic. The crux of the matter is that any vaccine works by enabling the immune system of a vaccinated person to suppress virus replication.
"What we cannot say with certainty is that the reduction in the virus in a vaccinated person will mean that they definitely cannot at any stage transmit the virus", Evans underscores. "It is certainly possible that after an initial infection, while the body's immune system is working against the virus, that in the early stages of that process someone could be infectious".
For his part, Jin Dongyan believes that those who were infected with SARS-CoV-2 but had no symptoms may need a booster vaccination at some point to elicit a stronger immune response.
"Asymptomatic people who were previously infected by SARS-CoV-2 should be in a group with very low priority to receive the vaccine", he suggests. "These people might already have immunity against the virus. The best vaccine is a natural infection that does not cause disease or causes a very mild disease".
It's not absolutely clear whether those immunised might still be infected but not develop symptoms, argues the expert, adding that it is also "well possible".
"It is not completely known if the vaccine provides sterilising immunity or just protects against [the] development of symptoms", the virologist says. "However, even if it is non-sterilising, the infection might be more restricted to the nasal cavity and the window of virus shedding is much shorter. More investigations are required to find out".
"We still need to see the results for asymptomatic infections", admits Andrew Hill referring to Pfizer's BNT162b2. "We need longer-term follow up to estimate how long protection lasts".
The academics unanimously agree that it will take a lot of time to clear up all the unknown issues about Pfizer's vaccine and other drugs entering the market amid the COVID pandemic.
"There should be head-to-head clinical trials set up, to compare the duration of protection between the leading vaccines", Hill emphasises. "This is very important, because millions of people will be given these vaccines worldwide. We need head-to-head trials to compare their protective effects and their safety reliably".
It will need another year of follow-up to see if clinical protection lasts two years and so on, according to Evans.
"We clearly need to have studied people for a year following vaccination to see if clinical protection lasts for a year and we haven't yet had people studied for more than 6 months, so it will be another 6 months at least before we can comment on clinical protection at one year", he concludes.