COVID-19: How effective are the vaccines against coronavirus variants

All viruses mutate. That’s normal when cells replicate. But the new coronavirus is more prone to mutations, and that poses a challenge to COVID-19 vaccine-makers.

Why does the SARS-CoV-2, the virus that causes COVID-19, mutate easily? Researchers say the coronavirus has an unusually large RNA. Its RNA polymerase (the enzyme responsible for copying a DNA sequence into an RNA sequence) is error-prone, and hence frequent mutations occur during infections.

There are at least four significant variants in circulation; then, there are sub-types. Some of them are the UK variant (B.1.11.7), the South African variant (B.1.351), the Brazil strains (P1 and P2), and the original Indian variant (B.1.6.17), which has at least two sub-types. They could be more variants and sub-types: all these reflect the challenge of developing vaccines.

“The emergence of variants is the biggest threat to control of the pandemic,” according to Kathleen Neuzil, director of the Centre for Vaccine Development at the University of Maryland School of Medicine in Baltimore, US.

In a commentary on the New England Journal of Medicine, Neuzil wrote: “A coordinated global prevention-and-control plan is the only way forward. Global investments in vaccine science and technology must be accompanied by investments in public health, genomics and disease surveillance, and programmatic immunisation infrastructure to mitigate the effects of COVID-19 and future pandemics.”

The vaccine scenario is not so grim. According to the New York Times, eight vaccines have gained approval for full use, while six others have been given the green light for limited use. All of them are effective in reducing the severity of the infection, irrespective of the variant. And some of them have shown remarkable efficacy against the newer strains.

Let’s take a look at some of them.

Pfizer against the UK and South Africa variants

The Pfizer-BioNTech coronavirus vaccine is very effective against two dangerous strains — the B.1.351 (first identified in South Africa) and B.1.1.7 (first found in the United Kingdom), according to two studies published on Wednesday.

The study published in the New England Journal of Medicine focused on the Pfizer vaccine’s use in Qatar. In January, after months of relative calm, the Gulf nation was hammered by two variants — the British and the South African ones — in the second wave of the coronavirus.

Contrary to the lab research, RNA vaccines seemed to be very effective against the variants. People in Qatar who received two doses of the Pfizer vaccine were 75 per cent less likely to contract COVID-19 from the South African strain than the unvaccinated. And the vaccine seemed to offer near-total protection from severe disease caused by the strain.

Researchers from Weill Cornell Medicine and Hamad Medical Corporation in Qatar looked at the records of more than 200,000 people in Qatar’s national COVID-19 databases between February 1 and March 31, when around 50 per cent of infections were caused by B.1.351 and 44.5 per cent by B.1.1.7.

Qatar launched a mass immunisation campaign with the Pfizer vaccine on December 21, 2020. By March 31 this year, 385,853 people had received at least one dose, and 265,410 had received two doses.

The Pfizer vaccine efficacy against the UK variant was 89.5 per cent at least 14 days after the second dose. The effectiveness dropped to 75 per cent for the South African strain. In 97.4 per cent of cases, the vaccine prevented severe infections, including hospitalisations and deaths, irrespective of the SARS-CoV-2 variant.

Why reduced protection is not inadequate protection

“The reduced protection against infection with the B.1.351 variant did not seem to translate into poor protection against the most severe forms of infection (resulting in hospitalisation or death), which was robust, at greater than 90 per cent,” the researchers said, according to the New England Journal of Medicine.

“We’re talking about a variant which is probably the nastiest of all the variants of concern,” one of the study’s authors, Laith Abu-Raddad, an infectious disease epidemiologist at Weill Cornell Medicine-Qatar, said. “It’s not the 95 per cent we were hoping, but the 75 per cent is really great,” he added.

What the Israel study says

The second study was based on around 230,000 infections in Israel from January 24 to April 3. According to the study published in Lancet, the Pfizer vaccine was more than 95 per cent effective at preventing infections for people who have received both vaccines. It also worked well among those 85 or older, at more than 94 per cent efficacy.

The British variant caused around 95 per cent of cases in Israel, but the country had vaccinated more than half of its population.

Although two doses of the vaccine provided robust protection, the Israeli study showed that even one dose of the vaccine was 77 per cent successful in preventing death.

Moderna against South African and Brazil strains

Moderna reported that a booster shot of its RNA vaccine could safeguard against coronavirus variants from South Africa and Brazil (P.1) if the recipients had completed the two-dose regimen. In a statement on Wednesday, the US vaccine-maker said a booster dose formulated specifically for B.1.351 (South African) was more effective.

The statement comes on the heels of results from a Phase 2 trial of 40 people vaccinated six to eight months before the booster dose. The trial evaluates three booster vaccines — one for B.1.351, a multistrain version, and its original vaccine.

“The strong and rapid boost in titers to levels above primary vaccination also clearly demonstrates the ability of mRNA-1273 [original Moderna vaccine] to induce immune memory,” Moderna Chief Executive Officer Stephane Bancel said in the statement.

Novavax against South African and UK variants

The Novavax vaccine protects against the newer variants B.1.1.7 and B.1.351, results from clinical trials show.

After Phase 2b trials in South Africa, Novavax said the new study, which confirmed its earlier findings, showed an efficacy of 51 per cent against infections caused by B.1.351 among people who were HIV negative, and 43 per cent in a group that included people who were HIV positive. The results were published in the New England Journal of Medicine on Wednesday.

“We have found that a prototype-sequenced NVX-CoV2373 [Novavax] vaccine was efficacious and induced notable cross-protection during a pandemic with a dominant circulation of the B.1.351 variant,” the researchers wrote in the journal.

In March, Novavax said its trials in Britain showed an efficacy rate of 96 per cent against the original coronavirus and 85.6 per cent against s B.1.1.7. But in South Africa, the efficacy was only 49 per cent against B.1.351.

Johnson and Johnson and the variants

The Janssen single-shot vaccine from Johnson and Johnson too is effective against variants first found in South Africa and Brazil, according to studies published in the New England Journal of Medicine.

The study across three continents showed the vaccine prevented hospitalisation and death 28 days after receiving the jab. It was 67 per cent effective against moderate to severe infection 14 days after vaccination and 66 per cent effective 28 days post-vaccination.

The April results are consistent with the numbers reported by Johnson and Johnson in January.

In South Africa, where the B.1.351 variant is predominant, the Janssen shot was 64 per cent effective against moderate to severe infection. It offered 82 per cent protection from severe COVID-19, 28 days after the vaccination.

In Brazil, where the P.2 variants are found in 69 per cent of cases, the Janssen jab gave 68 per cent protection against moderate COVID-19 and 88 per cent effective against severe infection.