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UK Government-Funded COVID-19 Vaccine Phase I/II Trials Report Positive Data

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A new COVID-19 vaccine candidate – VLA2001 – developed by Valneva has shown positive results in a UK Government-funded Phase I/II clinical trial, according to a press release.

VLA2001: A new candidate for fighting COVID-19?

Although some vaccines against SARS-CoV-2 have now been approved and rolled out in several countries, the development of new vaccine candidates has yet to drop its pace.

An example is VLA2001, developed by the French biotech company Valneva. How is it different from existing vaccines?

“The vaccine, to be produced in Scotland, is quite different from the currently-available vaccines,” explained Dr Peter English, consultant in communicable disease control and immediate past chair of the BMA Public Health Medicine Committee.

“The vaccines we currently use in the UK are very similar to each other… generating mRNA, which cells use to build the SARS-CoV-2 spike protein; and this protein is then secreted by the cells, where it stimulates the immune system to recognise it as an 'antigen', and to respond to it, so that if the actual virus is ever present, the immune system can immediately recognise and kill it.”

In comparison, English said VLA2001 is much more “traditional”; it uses whole inactivated SARS-CoV-2 viruses and adjuvant to stimulate an immune response – this is a commonly-adopted approach that is used for vaccines against diseases such as polio and influenza.

How was the trial conducted?

As a dose-ranging study, the trial aimed to evaluate three different dose levels of VLA2001 for their safety, tolerability and immunogenicity; this can help determine which dose may be the most effective. 153 healthy participants aged between 18-55 years were randomly assigned to one of three groups: receiving either a low, medium or high dose of the vaccine. Participants received two doses of their assigned dose, three weeks apart.

Approximately two weeks after receiving the second dose, participants were assessed for their levels of SARS-CoV-2 antibodies. The results showed a dose-dependent response to VLA2001; although more than 90% of participants across all dose groups had developed significant levels of antibodies to the SARS-CoV-2 spike protein, the geometric mean titres (GMTs) for both IgG and neutralizing antibodies were statistically significantly higher in the high dose group.

Further supporting a dose-dependent response, two weeks after the second dose, the geometric mean fold rise in antibodies from baseline was 86 in the high dose group, compared to 26 in the medium dose group. The seroconversion rate was also highest in the high dose group, achieving 100% seroconversion for IgG antibodies, 10.2% higher than the medium dose group.

In addition, VLA2001 was generally well tolerated regardless of dose level, with no reports of serious adverse events.

“These are great results from Valneva,” Clive Dix chair of the UK’s Vaccine Taskforce said in a press release. “Particularly around the antibody and cellular responses generated and low numbers of adverse events, as these indicate good levels of immune responses among the participants to date. The findings of 100% levels of immunogenicity against the viral spike protein in the high-dose group is also encouraging.”

What is next for VLA2001?

According to the press release, the study is not yet complete – six months after receiving the second dose, participants will be followed up to make further assessments of safety and immunogenicity. However, as a result of the positive data from the Phase I/II trial, Valneva is planning Phase III trials of the higher dose of VLA2001 at the end of April 2021.

“If the results from the Phase 3 clinical trials are positive and the vaccine meets the robust standards of safety, quality and effectiveness of our medicines regulator, the MHRA, this will be another powerful weapon in our arsenal to beat this pandemic,” commented UK Vaccines Minister Nadhim Zahawi.

Its ability to combat emerging variants of SARS-CoV-2 may also be explored.

“Valneva’s vaccine uses the whole virus, not just the spike protein. This means that the immune system is likely to create an immune response to other parts of the virus that are not included in the mRNA and vector vaccines currently in use. We do not yet know whether this will make any difference; but in theory it might, possibly, provide better cross-protection against variant strains, and/or better protection against infection, not just against illness,” English concluded.