GSK and Sanofi report positive data from COVID-19 vaccine candidate trial: Strong immune responses seen in adults of all ages

By Jane Byrne

- Last updated on GMT

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© GettyImages/

Related tags Gsk Sanofi BARDA COVID-19

Sanofi and GSK announced today that their COVID-19 vaccine candidate demonstrated strong immune responses across all adult age groups in a Phase 2 trial.

The investigational COVID-19 vaccine uses the same recombinant protein-based technology as one of Sanofi’s seasonal flu vaccines, along with GSK’s established pandemic adjuvant technology.

The drug companies had hoped to have regulatory approval for their jab in the first half of this year, but interim results from a Phase 1/2 study, released in December 2020, had shown an “insufficient”​ response in the over-50s, the age group deemed at higher risk for contracting the severe form of the virus. 

The interim results from the phase 2 trial on the vaccine, published today, on the contrary, showed a “strong neutralizing antibody response”​ in all adult age groups, and raised no safety concerns, triggering a move to next stage, phase 3.

The companies also noted a high immune response after a single dose of the shot in patients with prior infection, indicating, they said, strong booster potential for the jab.

Our Phase 2 data confirm the potential of this vaccine to play a role in addressing this ongoing global public health crisis, as we know multiple vaccines will be needed, especially as variants continue to emerge and the need for effective and booster vaccines, which can be stored at normal temperatures, increases,” ​said Thomas Triomphe, executive vice president and global head of Sanofi Pasteur.

The Phase 3 study on the vaccine is expected to start in the coming weeks. That trial is set to enroll more than 35,000 adult participants from a broad range of countries and will assess the efficacy of two vaccine formulations against variants that first emerged in Wuhan (D614) and South Africa (B.1.351).

Pending positive outcomes of that trial and regulatory reviews, the companies anticipate their vaccine being given emergency use approval in the fourth quarter of 2021.

Phase 2 study  

The full results of the Phase 2 study, which was supported by federal funds from US government agency, BARDA, are set to be published in a peer-reviewed journal.

Beginning in February 2021, the trial enrolled 722 volunteers in the US and Honduras. It included equivalent numbers of adults 18 to 59 years and those 60 years and above.

The randomized, double-blind, multi-center-dose-ranging study was conducted in healthy adults aged 18 years of age and older, including participants with high risk medical conditions, to evaluate the safety, reactogenicity, and immunogenicity of two injections given 21 days apart, with 3 antigen dose levels of 5, 10 and 15 µg.

The interim findings show that the adjuvanted recombinant vaccine candidate triggered a strong immune response amongst adults of all age groups with 95% to 100% seroconversion rates and neutralizing antibodies that were comparable to those generated by natural infection, said the partners.

The high titers observed in the non-naïve population after one dose of the vaccine candidate also suggest it may have strong potential for use as a booster vaccine, they added

Vaccine manufacturing support 

In addition to the collaboration with GSK, Sanofi is developing a messenger RNA vaccine in partnership with Translate Bio. In March 2021, Sanofi and Translate Bio initiated a Phase 1/2 clinical trial of their mRNA COVID-19 vaccine candidate, in order to assess safety, immune response and reactogenicity, after preclinical data showed high neutralizing antibody levels. First results are expected in the third quarter of 2021.

Sanofi is also providing manufacturing support to other vaccine producers. The company recently announced it will manufacture up to 200 million doses of Moderna’s COVID-19 vaccine for the US, starting in September 2021. Earlier this year, Sanofi said it would provide support to BioNTech for the supply of 125 million doses to the EU. In February, it reported it was supporting Johnson & Johnson in its COVID-19 vaccine production at a delivery rate of around 12 million doses per month.

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