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8h ago
By Anne Moore
President Vladimir Putin recently announced that a team of Russian scientists had developed a Covid-19 vaccine and that it had been approved for use by regulators, at least in Russia.
However, the announcement caused consternation among scientists and doctors around the world, as human trials of the vaccine, dubbed Sputnik V, had only started a couple of months before Putin’s announcement.
The results of phase one and two human trials of this vaccine have just been published in The Lancet. So what have we learned?
First, let’s see what kind of vaccine this is. The vaccine “platform” used in this study used adenovirus. These common cold viruses, called Ad5 and Ad26, protect themselves and cannot grow in the body. They only work to deliver the genetic code for one of the new coronavirus proteins, called a spike protein, to a cell.
By injecting people with these modified adenoviruses, the immune system is stimulated to respond to the spike protein at the time of immunization, and hopefully to respond for many years to come, if the immunized person is exposed to the coronavirus. causing Covid, known as SARS-CoV-2.
This is not a Sputnik moment
The vaccine platform the Russians use is not new. Some of the major Covid-19 vaccines use adenovirus, including the University of Oxford vaccine and an Ad26 vaccine developed by Johnson and Johnson. After successful animal trials, both are being tested in humans. CanSino Biologicals, a Chinese company, has also shown that its Ad5 vaccine is safe and induces immunity against coronavirus in humans.
However, the Russian group has shown that their stable, lyophilized vaccine preparation works to the same extent as their frozen liquid vaccine preparation. This is important for shipping and implementing a vaccine.
The Lancet document describes acceptable safety data, even with the high dose used. These safety results are not unexpected as the safety of various adenovirus-based vaccines for different diseases has been demonstrated in previous research.
So it’s safe, at least in healthy people ages 18 to 60, but does it work? Does it protect against Covid-19?
The Russian group showed that their vaccine induces high levels of antibodies that can bind to the spike protein. But a more important measure is the level of antibodies that are functional. That is, can antibodies prevent or neutralize the infection of a virus in a cell?
Neutralizing antibody levels were quite low in this study, compared to other published vaccine trials. So were T-cell responses (the other arm of the adaptive immune system response).
One interpretation of this is that these vaccines do not induce good neutralizing protection. Alternatively, the methods used to measure these immune responses may not have been optimal. In the absence of international reference standards, we cannot say if this vaccine is better or worse compared to others.
Fundamentally, as with other clinical trials of the Covid-19 vaccine, we do not know if that level of neutralization is sufficient to protect against infection and how long these antibodies remain in the blood. The post shows responses only up to a month after immunization. The fundamental question of whether these vaccinated people are protected against Covid-19 was not a central topic of this article.
Ready for mass deployment?
Despite the positive results of the small phase one trial of the Sputnik V vaccine, it must be tested in a much larger group of people before it can be used in an entire population with confidence.
All vaccines must be tested in large numbers of people, of different ages and ethnicities, in phase three clinical trials. Phase three trials are necessary to gain a high level of confidence that the vaccine protects against infection. They also help detect rare side effects that may not be apparent in a small group of healthy volunteers. This final stage of testing is not one that can or should be left out.
Unfortunately, Sputnik’s nickname highlights the politicization of serious scientific and medical efforts to develop vaccines against Covid-19. This “vaccine nationalism” is of great concern to everyone in the field of vaccines who understands the power of vaccines to eliminate disease, but only when used with the acceptance of the public.
The conversation
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