On Tuesday, Paul Offit, the vaccine developer and a professor of pediatrics at Children’s Hospital of Philadelphia, dropped by, virtually, for a conversation with STAT+ subscribers. During the discussion, he addressed a question on everyone’s mind: How worried should we be about new variants of SARS-CoV-2, the virus that causes Covid-19?
Offit — who, overall, believes “we’re going to turn the corner,” with the help of vaccines — had plenty of worries. A rare side effect of the vaccines could emerge and scare people away from them, even when the benefits far outweigh its risks. It could take a long time to fix vaccine distribution and manufacturing problems.
But he said his biggest concern is that a new variant of the SARS-CoV-2 virus will learn to evade the vaccines. He also explained, at length, why he doesn’t think it’s time for you to worry yet. The transcript of that explanation follows; it has been edited for clarity and length.
Offit: So this is a bat coronavirus — it’s not a human coronavirus — that made its debut in the human population in November 2019. It will adapt to growth in humans, and when it adapts, it will create variants. It created a variant the minute it left Wuhan, the so-called 614 variant, which was somewhat more contagious. Since then, it’s created at least four variants that we know of — the U.K. variant, the South African variant, the Brazilian variant and then, just in the last few days, the California variant.
So the critical question is not are variants being produced. Of course they’re going to be produced. The critical question is do these variants make the virus more contagious, more virulent, and most importantly, far and away most importantly, have these variants evaded recognition by vaccine-induced immune response? That’s the critical question.
Here’s what I would say. It looks like the U.K. variant is somewhat more contagious. The good news is it’s still spread by small droplets, so masking and physical distancing still work. I don’t think there’s good evidence that the U.K. variant is more virulent. If you look at people who are hospitalized in the U.K., you are no more likely to die if you’re hospitalized with a variant strain or not. That may change over time.
The critical question is, have these viruses mutated away from the vaccine? The way you’re going to know that, the proof for that, is when you see people who have gotten two doses of vaccine who are then hospitalized and who are shown to be infected with a variant strain. That’s the proof. Everything else that we’re looking at is just a way to predict whether or not that happens. And the predictions are not perfect.
So, for example, if you look at the U.K. variant, both Pfizer and Moderna have taken serum from people who were immunized with their vaccines and shown that those sera neutralize the U.K. variant in the same manner that they neutralize the non-variant viruses. So therefore one should be reassured.
But if you look at the South African variant, it looks like when the companies take the sera from people who were immunized with their vaccines and see whether you can neutralize that South African variant in the laboratory, it shows that there’s a decreased capacity of those antibodies that are obtained from people who are immunized to neutralize that virus. Now, it’s unclear what that means. Just because you have a lesser capacity to neutralize that virus doesn’t mean that you’re not still protected. Because we don’t really know the level of neutralizing antibodies that’s associated with protection. Even though it’s a lesser response, that doesn’t mean it’s still not an adequate response.
The second thing is you’re just looking at one aspect of the immune system, which is neutralizing antibodies. There are other aspects of your immune system that are associated with protection. One is called T-helper cells, which are a kind of T cells that actually help your B cells make antibodies. And those are much more broadly cross-reactive. The second thing is so-called cytotoxic T cells, which are T cells that kill virus-infected cells. All three of those parts of the immune system are important for protection or at least amelioration of disease. And we’re only looking at neutralizing antibodies when we’re doing these studies.
So I would say, don’t worry yet. We don’t really have any evidence that people who have been given two doses of these vaccines are at greater risk. We’ll see what happens with the South African strain. Interestingly, studies of unapproved vaccines are being done now in South Africa. So we’ll see whether or not people who get those vaccines in South Africa are relatively protected against this strain. We’ll know this over time. But I would say don’t worry yet.