A day after Moderna vaccine results, rumors swirl of pending AstraZeneca data
A day after Moderna and the NIH published much-anticipated data from their Phase I Covid-19 vaccine trial, attention is turning to AstraZeneca which, according to a UK report, is expected to publish its own early data tomorrow.
ITV’s Robert Peston reported that AstraZeneca will publish the Phase I data in The Lancet.
AstraZeneca and Moderna represent the two most ambitious Covid-19 vaccine efforts, having set the quickest timelines for approval (though they were recently joined in that regard by the Pfizer-BioNTech partnership) and some of the loftiest goals in total doses. Yet there is even less known about AstraZeneca’s vaccine’s effect on humans than there was about Moderna’s before yesterday. Although, in a controversial move, Moderna released some statistics from its Phase I in May, AstraZeneca has yet to say anything about what it saw in its Phase I trial — a move consistent with the scientific convention to withhold data until it can be published in a peer-reviewed journal.
Instead, so far what the world knows about the effects of a vaccine that the US, EU, UK and a significant portion of the developing world have signed agreements for — billions of dollars for billions of doses — can be reduced to a primary study and the comments so far from scientists at Oxford University, where the vaccine was first developed, and company executives.
Those scientists and executives have been laying the case, most recently in a lengthy Bloomberg feature released today, that when it comes to their vaccine, people should focus on the T cell response rather than antibodies. Although vaccines work both by eliciting both a T cell response and neutralizing antibodies from B cells, investigators generally focus on antibodies, in part because they are easier to measure. Moderna called its Phase I a success in part because trial subjects made more neutralizing antibodies than patients who had been infected with the virus.
Recent comments from AstraZeneca appear designed to lower any expectations that they would show similar results. “Neutralizing antibodies is one of the things you’ll look at,” AstraZeneca R&D chief Mene Pangalos told Bloomberg, “but the T-cell response is going to be important.”
Peston cited an unnamed source who told him, “Everybody is focused on antibodies but there is a growing body of evidence suggesting that the T cells’ response is important in the defence against coronavirus.”
Adrian HillTalk of AstraZeneca and antibodies began after early critics pointed out that the animal data supporting AstraZeneca’s Phase I didn’t find high levels of antibodies. In that primate study, conducted at NIAID’s Rocky Mountain Laboratories in Montana, investigators inoculated six rhesus monkeys with the experimental vaccine and exposed them to high doses of SARS-CoV-2 28 days later. The monkeys showed no signs of pneumonia or disease, a result that Adrian Hill, one of the two scientists who developed the vaccine, told Bloomberg “wasn’t promising — it was fantastic.”
William Haseltine, a former professor at Harvard Medical School and HIV researcher, wrote in Forbes that the vaccine likely wouldn’t be protective because the monkeys didn’t produce high levels of antibodies. He raised the specter of people who were protected from developing the disease but still capable of spreading the infection to others. AstraZeneca and Oxford scientists countered that the vaccine didn’t need to produce high levels of antibodies if it produced a T cell response, and that it wasn’t fair to compare monkeys exposed to massive doses of the virus to real world scenarios anyway.
Sarah Gilbert“No one knows how strong the immune response needs to be to achieve protection in people of any age,” Sarah Gilbert, the principal Oxford scientist behind the vaccine, told Bloomberg. “If we get a strong T-cell response, we don’t need such a high neutralizing antibody titre to achieve protection.”
These questions of just how protective vaccines are, if they might inoculate someone from disease but still allow them to spread the virus, and how long immunity might last, will likely be debated for months. But a much better test for the data is coming. AstraZeneca has already begun one Phase III trial in Brazil and will soon begin another in the US. Moderna will launch its Phase III on July 27th. These studies, conducted on tens of thousands of people, will examine T cell response and antibodies but the more important question will be simpler: Do people inoculated with the vaccine become sick, or not?
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