Covid-19 vaccine: pharmaceutical firms focus on 501.V2 variant
The 501.V2 variant has been a curveball for vaccine developers across the globe, with all asking the same question: will our vaccine be the one to vanquish this highly transmissible variant?
Professor Salim Abdool Karim, who heads the Centre for the Aids Programme of Research in SA as well as the ministerial advisory committee on Covid-19, said that about six weeks ago, the minister of health asked him to contact vaccine companies to check what data they had on their vaccines' efficacy against the 501.V2 variant that is dominant in SA.
"I contacted all of them and spoke to chief scientific officers, and at that stage nobody had data. That was before the Novavax results were out," he told the Sunday Times this week.
He said that from there, "arrangements were made for us to send the virus from the Durban office so assays could be done".
In other cases, blood from trial participants was sent to SA for the assays to be done here.
"We are doing it for two or three of the vaccines, and the companies have done it themselves for others," he said.
In the case of Sinopharm, it turned out that someone in China had travelled to SA and caught the variant that's dominant here, "so they could grow it themselves and do tests there", said Abdool Karim.
He said that if a vaccine's ability to neutralise the virus is diminished tenfold or more when it encounters a different variant, that is when the scientists get concerned.
In the case of the Pfizer vaccine, diminished neutralisation was about threefold.
"Even though you need threefold higher levels of antibodies to neutralise our variant for the Pfizer vaccine, it doesn't seem to be a problem at all. Based on that, I am pretty confident - though not 100% sure - that the Pfizer vaccine could work if it can do it in a test tube in that way."
He said that the Sinopharm vaccine only showed a 1.6-fold diminished neutralisation against the variant, and that this also gives him "more confidence".
"Neutralisation is not a confirmed correlate of protection, but it's the best we have right now."
The Moderna vaccine showed a 6.4-fold decline but that too is "not something I am overly concerned about. It's when it is tenfold or higher that I get concerned," he said, adding that definitive lab results are still awaited for the Johnson & Johnson vaccine and for Sinovac.
Vaccine companies are also working hard at booster shots that can help tackle the 501.V2 variant.
"I am expecting those to become available in the next few weeks," said Abdool Karim, "Moderna's will probably come out first and we are in communication with them."
He said that vaccines that use mRNA technology lend themselves more easily to booster shot development.
This puts Moderna and Pfizer at an advantage.
"They are definitely working on boosters for the 501.V2 variant, so, based on what they produce, we expect those will go into animal studies.
"For boosters, you don't need to do clinical trials - you show it through the antibody response in the lab and then do animal studies," he said.
I think next we are going to see a completely new generation of vaccines that are going to be quite differentProfessor Salim Abdool Karim
Animals will be vaccinated and then scientists will test to see how it neutralises this particular variant.
It takes six to eight weeks to develop a booster for an mRNA vaccine, but it's not that easy to do that with live viral vectors, so "AstraZeneca and Johnson & Johnson are making them, but it will take a little longer - around three to four months".
But, said Abdool Karim, "the field is changing fast".
"I think next we are going to see a completely new generation of vaccines that are going to be quite different. They will generate broader immunity: they'll be engineered to target areas that are likely to escape mutations."
Ultimately, "when you look at our needs in response to Covid-19, we need a vaccine that is long-lasting, gives broad immunity, and covers us against many variants".
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