Covid-19 immunity: New coronavirus variant increases risk of reinfection, says local expert

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  • Newer coronavirus variants are spreading more easily and quickly among people, causing more Covid-19 infections 
  • Researchers have been studying the immune response of individuals who were infected in the first wave as it has implications for two things, one being reinfection
  • Some vaccines have also shown to be less effective against the new variant in SA, but additional studies testing this are underway

The new coronavirus variants that have emerged are rattling the world as they've been shown to escape antibodies elicited by previous, natural infection and Covid-19 vaccines.

Professor Penny Moore, the South African research chair of Virus-Host Dynamics at Wits University and the National Institute for Communicable Diseases (NICD), however, believes that these variants should not have come as a surprise and thrown scientists off balance, as virus mutations constantly arise.

And millions of people being infected has resulted in endless opportunities for the virus to become “fitter” and better, she said on Thursday during a webinar on the update of the vaccine rollout in SA and the impact of the variant.

The original virus first detected in Wuhan, China in December 2019 is identified as the root of the SARS-CoV-2 virus, but the further it has moved away from this root over time, the more mutations the virus has accumulated, explained Moore.

As it stands, three variants have a worrying number of mutations, and those that have come to dominate are known as the variants of concern (VoC). They are:

  • The 501Y.V1 variant first identified in the UK which has spread to over 90 countries 
  • The 501Y.V2 variant first identified in South Africa which has spread to over 40 countries 
  • The 501Y.V3 variant first identified in travellers from Brazil which has spread to more than 30 countries

In South Africa, 501Y.V2 has become the dominant virus and has been responsible for more than 90% of infections in the second wave. According to experts, this virus is more infectious than the original virus variant, D614G, from the first wave.

Immunity to SARS-CoV-2

When looking at immunity to SARS-CoV-2, scientists are particularly interested in what is known as “neutralising antibodies” – a particular subset of antibodies (derived from natural infection or vaccination) that are able to bind to the virus and stop it from infecting cells. These antibodies are critical for preventing Covid-19 infection, said Moore.

Can people be reinfected?

Moore and colleagues conducted a study to find out whether the antibodies in people who were infected with the original variant are protective against 501Y.V2, as this has implications for two things: the individual’s ability to resist reinfection, and whether vaccines will be effective against this new variant.

Moore and her team therefore looked at samples from 44 convalescent blood plasma donors (people who had Covid-19 during the first wave of infection and recovered).

The researchers then tested the ability of this blood plasma to neutralise the new variant, but found that the antibodies were much less effective against 501Y.V2.

“Almost all of these individuals had much less activity against the new variant than they had against the original variant that infected them,” she said. In other words, these individuals might be susceptible to reinfection with the new variant.

What does this mean for vaccines?

Results for three vaccines testing their efficacy (how well a product works) against 501Y.V2 in a clinical trial have recently been released. These vaccines are the ones produced by Oxford-AstraZeneca, Novavax, and Johnson & Johnson.

“In all three cases, although they showed pretty good efficacy globally, there was a substantial knock in efficacy [against 501Y.V2] when it was tested in South Africa,” said Moore.

The very low efficacy results of the AstraZeneca vaccine against mild to moderate disease caused by the new variant resulted in its rollout being suspended earlier this month, with the SA government making a switch to the J&J vaccine. This vaccine is currently being administered to healthcare workers countrywide.

“So it does seem that we potentially have a problem in the ability of our vaccines to work against the 501Y.V2 variant, though we should speak more about whether this translates to protection from severe disease,” Moore added. 

As it stands, we don’t yet have clinical data on how well the AstraZeneca and Novavax vaccines protect against severe disease and hospitalisation caused by the new variant. This is the data we need, as severe disease and hospitalisation are what we’re trying to avoid.

Lab and clinical data of AstraZeneca vaccine consistent 

In addition to being tested in a clinical study, the AstraZeneca vaccine was also tested in a laboratory setting where participants who were vaccinated with this vaccine had their blood samples taken to be assessed against the new variant.

The researchers found that almost all of these samples failed to neutralise the new variant.

“In this case, 78% of the AstraZeneca [samples] showed absolutely no neutralisation [against] 501Y.V2. And it is this, combined with the clinical data … that resulted in the suspension of the AstraZeneca rollout in SA,” said Moore.

Unfortunately, we don’t yet have the equivalent laboratory data for the J&J vaccine and Novavax vaccine, although we have clinical trial data. But both vaccines have lab studies underway, she explained.

Complex situation

“We have this awkward situation where we have laboratory and clinical trial data for AstraZeneca, and we have clinical trial data for J&J but we don’t have laboratory data. And so it becomes very difficult for us to understand … which vaccines are the ones to move forward with and which are the ones that we need to worry about,” said Moore.

She explained that Moderna and Pfizer, the two mRNA Covid-19 vaccines, have also been tested against 501Y.V2 in labs. And while these vaccines also “took a substantial knock against 501Y.V2”, their saving grace was that they elicited much higher titers, meaning there was still some neutralisation activity.

“In this case, we have some pretty compelling lab data that suggest that they might be efficacious, but we have so far no clinical trial data [of the Moderna and Pfizer vaccines] against the variant.” Moore said that every vaccine is different and that one can’t extrapolate from one to the next. To understand what’s needed, both lab data and (especially) clinical trial data are needed, although the latter is challenging and expensive to carry out.

However, it is likely that as newer mutations arise, vaccines will have to be updated periodically, as is the case with the flu shot, she said.

“There’s a lot we know – we understand the problem – but there’s also a lot we don’t know. But the silver lining is that we’ve never moved this fast in response to a pathogen, ever. We’re in a much better place to tackle both new variants as they emerge and also new pathogens than we have ever been before,” she said.

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