The first real-world data for COVID-19 vaccines is in – and the vaccines’ effectiveness have once-again shot past scientists’ expectations.
Vaccines are typically less effective in the real-world than in clinical trials. But in data from Israel and the United Kingdom, both of whom have managed to vaccinate a large slice of their population, vaccine effectiveness appears to be matching that seen in clinical trials.
There are also positive signs the vaccines will significantly cut viral transmission, although it is too early to draw firm conclusions.
In Britain, Pfizer’s mRNA vaccine appears to be 88 per cent effective at preventing symptomatic infection in those aged over 80.
Israeli scientists are reporting a 92 per cent effectiveness rate overall – similar rates to those seen in clinical trials that initially stunned scientists.
“I find it surprising,” said Professor Simon Foote, director of the John Curtin School of Medical Research at the Australian National University. “But it’s a nice surprise.”
“There is absolutely no doubt that people who have been vaccinated are substantially less likely to get symptomatic disease. They are much less likely to end up in hospital. And they are probably much less likely to die of the disease.”
Israel and Britain are among world leaders in vaccinating their populations. Israel has managed to give one dose to least 56 per cent of its population, while in Britain about 30 per cent of people have received at least one jab.
Both countries faced surging epidemics only a month ago, but daily cases have now been substantially curtailed.
The US has also made strong headway, reducing its daily caseload from a peak of 314,172 on January 8 to 66,481 on March 4. About 16 per cent of the US’s population had received a dose of vaccine.
However, these countries’ success was likely linked to more lockdowns and perhaps the end of winter, rather than the effects of vaccination, said James Wood, associate professor at the School of Population Health at the University of NSW.
Britain went into a national lockdown at the start of January, while Israel’s national lockdown started at the end of December. Israel’s progress appears to be plateauing, however, even as restrictions are eased.
Professor Wood estimated a country would need to give two doses of vaccine to at least 20 to 30 per cent of the population before there was a significant impact on infection rates. Israel’s success may partially be explained by their vaccination numbers, he said.
“If you go completely open when you don’t have a lot of vaccine coverage, you’re going to see rises again. You still have people who are unvaccinated who are at risk – and they are at higher risk now because you’re letting infection spread,” he said.
The vaccines work
Vaccine efficacy describes how well a vaccine works in a clinical trial. But a vaccine’s effectiveness – how well it works in the real world – is a different matter.
Vaccine trials enrol select groups of patients. Pfizer’s phase 3 trial, for example, excluded patients with uncontrolled chronic medical conditions.
In the real world, “you’re going to have people who would not have met the eligibility of the trials: older people, pregnant women, people with underlying health conditions, who are getting the vaccine. The chances are the effectiveness would be different from a very controlled trial,” clinical trial expert Professor Tammy Hoffmann told The Age in February. “Probably less; by how much, we just don’t know.”
But Pfizer’s vaccine appears to have held up. In a large, high-quality study drawing data from almost 1.2 million people in Israel (excluding nursing home residents and healthcare workers), the vaccine was 92 per cent effective at protecting against symptomatic COVID-19 and preventing severe disease from seven days after the second dose, similar to results seen in clinical trials.
Importantly, the study includes data from almost 80,000 vaccinated people aged over 70 – a group at high risk of serious illness and death.
Nearly all cases of COVID-19 in Israel come from the variant first spotted in Britain; the vaccine’s strong performance suggests it will cover this variant with ease.
In England, public health authorities have reported Pfizer’s vaccine is 88 per cent effective in those aged over 80 from seven days after the second injection. Infection and death rates in this group are down across the country.
In Scotland, a single dose of Pfizer’s vaccine was 85 per cent effective at reducing COVID-19 hospitalisations; AstraZeneca’s vaccine did even better, although there is significant uncertainty around those numbers.
“The bottom line is it’s really good news. We now have clearly effective tools against the worst effects of COVID,” said Professor Wood.
“This is going to allow us to start the move out of the emergency situation.”
But we still don’t know if they will stop the pandemic
To bring COVID-19 under control and return to something close to normal life, we need to both stop people dying and stop the virus moving through our community.
Conclusive studies showing vaccines cut transmission are hard to do, as scientists have to devise ways of showing a person did or did not pass on a virus.
But there are several data points that now all point in the same direction.
In a study of 20,641healthcare workers in England mainly given Pfizer’s vaccine, the vaccine was 85 per cent effective at stopping infection from seven days after the second dose.
Importantly, many people in this study were tested twice a week for COVID-19 even if they did not have symptoms; the strong results suggest the vaccine really is stopping infection altogether (rather than just protecting people from falling sick), the key step to stopping transmission of the virus.
And new Israeli data suggests people who are vaccinated have much lower levels of virus when they do become infected. The more virus someone has, the easier it is for them to spread it.
“Is the vaccine going to stop the spread of COVID? I think the jury is still out on that one, but this Israeli data suggests it is definitely going to decrease the infectiousness of people who get infected after being vaccinated,” said Professor Foote.