10m more COVID-19 vaccines for Aus; Russia's efficacy results

It’s been another busy week in the race to vaccinate the world against COVID-19, with the Australian Government acquiring another 10 million doses of Pfizer and BioNTech’s vaccine and Russia announcing promising phase 3 trial results.

Australian acquisition

On Thursday, the Australian Government announced that it had secured an additional 10 million doses of the Pfizer vaccine on the advice of The COVID-19 Vaccines and Treatments for Australia – Science and Industry Technical Advisory Group, led by Professor Brendan Murphy. This latest acquisition means Australia will now receive 20 million Pfizer doses in 2021 and has access to over 150 million vaccine doses from four separate agreements.

The government said the vaccination program remains on track for commencement of delivery in late February to people in the first priority group, Phase 1a. This includes aged-care and disability-care residents and workers, frontline healthcare workers, and quarantine and border workers.

The Australian Government is also extending free access to COVID-19 vaccines to all visa holders in Australia. This will include refugees, asylum seekers, temporary protection visa holders and those on bridging visas. People currently residing in detention facilities will also be eligible, including those whose visas have been cancelled.

“It is vital that we offer vaccines to all people living in Australia to achieve the maximum level of coverage,” Prime Minister Scott Morrison said.

Russian results

The acquisition came just two days after preliminary efficacy and safety results from Russia’s own COVID-19 phase 3 vaccine trial were released, suggesting that the two-dose regimen of the adenovirus-based vaccine (Gam-COVID-Vac, also known as Sputnik V) is 91.6% efficacious against symptomatic COVID-19.

Published in The Lancet, the trial was conducted across 25 hospitals and polyclinics in Moscow. The primary interim efficacy analysis reports on results from almost 20,000 participants: 14,964 in the vaccine group and 4902 in the placebo group. The ongoing trial is aiming to include 40,000 participants.

Gam-COVID-Vac is a two-part vaccine that includes two adenovirus vectors — recombinant human adenovirus type 26 (rAd26-S) and recombinant human adenovirus type 5 (rAd5-S) — which have been modified to express the SARS-CoV-2 spike protein. The adenoviruses are weakened so that they cannot replicate in human cells and cannot cause disease. Trial participants were given one dose of rAd26-S, followed by a booster dose of rAd5-S 21 days later; the authors explained that using a different adenovirus vector for the booster vaccination may help create a more powerful immune response compared with using the same vector twice, as it minimises the risk of the immune system developing resistance to the initial vector.

From 21 days after receiving the first dose (the day of dose 2), 16 cases of symptomatic COVID-19 were confirmed in the vaccine group (0.1%) and 62 cases (1.3%) in the placebo group — equivalent to an efficacy of 91.6%. The authors note, however, that because COVID-19 cases were detected only when participants self-reported symptoms (followed by a PCR test), the efficacy analysis only includes symptomatic cases of COVID-19, and further research is needed to understand the efficacy of the vaccine on asymptomatic COVID-19 and transmission. Furthermore, median follow-up was 48 days from the first dose, so the study cannot assess the full duration of protection.

No serious adverse events were deemed to be associated with vaccination, with most reported adverse events being mild, including flu-like symptoms, pain at injection site and weakness or low energy. Four deaths were recorded — three in the vaccine group and one in the placebo group — but none were deemed to be associated with vaccination, and two in the vaccine group had underlying conditions and developed symptoms of COVID-19 shortly after the first dose, suggesting they were already infected. A sub-analysis of 2000 adults older than 60 years suggests the vaccine is effective and well tolerated in this group.

As part of their secondary analyses, the authors explored the efficacy of the vaccine against moderate or severe COVID-19. At 21 days after the first dose, there were no cases of moderate or severe COVID-19 in the vaccine group and 20 cases in the placebo group, equivalent to an efficacy of 100% against moderate or severe COVID-19.

Although the study was not designed to assess the efficacy of a single-dose regimen, the findings hint to the early onset of a partially protective effect 16–18 days after a single-dose immunisation. From day 15–21, efficacy against moderate or severe COVID-19 was 73.6%, but further research is required to draw any robust conclusions from these observations. The research team has recently received approval to investigate the effectiveness of a single-dose regimen of the vaccine.

“Our interim analysis of the randomised, controlled, phase 3 trial of Gam-COVID-Vac in Russia has shown high efficacy, immunogenicity and a good tolerability profile in participants aged 18 years or older,” said co-lead author Dr Inna V Dolzhikova, from Russia’s Gamaleya National Research Centre for Epidemiology and Microbiology. The authors report a need for further research to investigate the vaccine in adolescents and children, as well as pregnant women.

Writing in a linked Comment, Professor Ian Jones from the University of Reading and Professor Polly Roy from The London School of Hygiene & Tropical Medicine added, “The development of the Sputnik V vaccine has been criticised for unseemly haste, corner cutting, and an absence of transparency. But the outcome reported here is clear and the scientific principle of vaccination is demonstrated, which means another vaccine can now join the fight to reduce the incidence of COVID-19.”

Image credit: ©stock.adobe.com/au/M.Rode-Foto

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