The announcement by pharmaceutical company Pfizer and tech company BioNTech that their coronavirus vaccine works to prevent Covid-19 has been welcomed globally, with no small sense of relief. But there are a number of outstanding issues that must be addressed before people will be rolling up their sleeves in anticipation of a jab.
The partnership is the first to report positive results from the final stage of clinical trials: the double injection was found to be more than 90 per cent effective in preventing Covid-19, based on 94 cases of the disease observed in an interim study.
But the word interim brings with it the first caveat: the clinical trial is not yet complete, and Pfizer/BioNTech have not published their data in full nor submitted findings to a peer-reviewed medical journal or to regulatory bodies.
Much is being made of the novel vaccine's putative 90 per cent efficacy, with Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, called the high percentage "just extraordinary." Most experts would have been happy with a 70 per cent effectiveness, while the US Food and Drug Administration (FDA) has set the bar even lower, saying any SARS -CoV-2 vaccine must be at least 50 per cent effective to get its approval.
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However the 90 per cent efficacy is based on two doses of the new vaccine being given three weeks apart. This double-dosing regime is a feature of some established vaccines. Two doses of the MMR (measles, mumps, rubella) vaccine are 97 per cent effective at protecting someone from measles, whereas a single dose is 93 per cent effective.
The only data we have at present is from a press release - it has not undergone 'peer-review' through scientific publication.
The preliminary results from the first SARS-CoV-2 trial suggest that if you took 10 people who were going to get sick from Covid-19 and vaccinated them, only one out of the 10 would now get sick.
Surely this means we should be excited?
Well, not quite. The only data we have at present is from a press release- it has not undergone “peer-review” through scientific publication. The study won’t be complete until 164 volunteers have confirmed Covid-19, and the estimate of efficacy may therefore change. The trial volunteers must be monitored for a defined period of time after vaccination for any side effects to be picked up. Because the vaccine uses new technology (mRNA) never before approved for human use, an allergy to a component must be carefully watched for.
Other important questions remain unanswered: how long will the protective effect of the vaccine last ( the 90 per cent effectiveness rate was calculated seven days after the second jab); will the vaccine work equally well in everyone (an earlier phase 1 trial with this vaccine showed that immune responses were lower in older people); and will it prevent transmission of the virus?
Then there are some practical issues. The new vaccine requires storage at a temperature below -70 degrees. This presents a global shipping challenge. And at a local level, it means the vaccine won’t be available from your family doctor. Vaccination centres with specialised freezing facilities will have to be in place before a coronavirus vaccination programme could begin.
One critic is concerned that vaccinated people could still become asymptomatic carriers and unknowingly spread the virus to others.
One of the severest critics of the breakthrough announcement is Dr William Haseltine, a retired Harvard professor and philanthropist. "This is science by public pronouncement," he said. Because the trial isn't structured to test volunteers for asymptomatic infection, Haseltine is concerned that vaccinated people could still become asymptomatic carriers and unknowingly spread the virus to others.
He is adamant that the announcement by Pfizer/BioNTech doesn’t mean an end to the epidemic. It certainly doesn’t mean we will see the end of our new public health practices. Controlling Covid -19 will still include some degree of social isolation, care with personal hygiene, and bursts of restricted movement.
Because, welcome as the vaccine breakthrough is, it is no magic bullet with which we can destroy the novel coronavirus.