Sanofi and Glaxo scrape a Covid vaccine latecomer

After a long wait the groups’ jab delivers mediocre efficacy.

Just as worldwide Covid cases have started to slide, Sanofi and Glaxosmithkline have finally reported phase 3 data with their vaccine contender. And the results are unimpressive, with 58% headline efficacy.

True, the companies’ jab did go through its pivotal trial at a very different time to most predecessors, with the presence of new variants making it particularly tricky to carry out a cross-trial comparison versus currently authorised vaccines. But the adjuvanted protein-based shot, which can be stored in the fridge, looks likely to be reserved for low to middle-income countries.

Perhaps this is not a bad thing: with wealthy countries already well into booster campaigns it is developing nations that need new options the most.

Full data from the phase 3 trial, called VAT08, will be published later this year. For now, Sanofi and Glaxo are just saying that the jab showed 58% efficacy against any symptomatic Covid, rising to 75% against moderate-to-severe disease, and 100% against severe disease and hospitalisation.

The companies did not give any data on deaths, raising the possibility that there were none.

Cross-trial comparison of selected Covid-19 vaccines
    Efficacy against Covid-19 Severe Covid-19 cases
Company Vaccine Vaccine Pbo
Pfizer/Biontech Comirnaty 95% 1 9
Moderna Spikevax 94% 0 30
Novavax Nuvaxovid 89% 0 1
Astrazeneca Vaxzevria  70% 0 2
Johnson & Johnson JNJ-78436735 66% 5 34
Sanofi/Glaxosmithkline Sanofi-GSK vaccine (SP0253) 58% 0 4
Note: Efficacy figures based on phase 3 studies when different variants were prominent. Source: company releases, Lancet & NEJM. 

On the face of it the Sanofi-Glaxo vaccine looks like the worst of the main Covid vaccine contenders, with efficacy falling below even that seen with Johnson & Johnson’s JNJ-78436735 and Astrazeneca’s Vaxzevria.

J&J’s jab has largely been relegated to the second tier, with most of its sales this year expected to come in low to middle-income countries.

Meanwhile, Astrazeneca’s Vaxzevria is not even available in the US. The company said in the middle of last year that it was planning to seek full approval there rather than emergency use authorisation. This has not yet happened, but a filing is expected in the first half of 2022, the group disclosed during its fourth-quarter earnings.

Delta data

However, the Sanofi-Glaxo vaccine looks to have done respectably against Delta: the groups said that early data indicated 77% efficacy against any symptomatic Covid associated with this variant.

This figure compares favourably against data with Vaxzevria and JNJ-78436735. Details on the latter’s performance against Delta are hard to come by, but a real-world study in South African healthcare workers found that it was 71% effective at preventing hospitalisations due to the variant – so presumably its efficacy against any symptomatic Covid caused by Delta will be lower.

Cross-trial comparison of selected Covid-19 vaccines' efficacy against Delta variant
Company Vaccine Efficacy against Delta Data source
Pfizer/Biontech Comirnaty/BNT162b2 


NEJM, Aug 2021
Moderna Spikevax/mRNA-1273 87% BMJ, Dec 2021
Novavax Nuvaxovid/NVX-CoV2373 82% Company release (paediatric population of Prevent-19)
Sanofi/ Glaxosmithkline Sanofi-GSK vaccine (SP0253) 77%* Company release (VAT08)
Johnson & Johnson JNJ-78436735 71%** Sisonke, S Africa real-world study 
Astrazeneca Vaxzevria/AZD1222  67% NEJM, Aug 2021
*"Early data", sequencing "still in progress"; **protection against hospitalisation from Delta variant.

On Delta, the Sanofi-Glaxo vaccine looks almost in line with Novavax’s Nuvaxovid, the other main protein-based vaccine. Nuvaxovid has the go-ahead in Europe and the UK, but is still awaiting US authorisation.

However, Delta is no longer the dominant variant, having been overtaken by Omicron – and Sanofi and Glaxo were quiet about how their vaccine fared against the latter. Sequencing is still “in progress” so more details might emerge; but perhaps VAT08, which began last May, did not capture many cases of Omicron. The companies previously said most subjects were enrolled in the third quarter of 2021, when Delta was rife.

Investors will also want more information on adverse events; all the companies are saying, for now, is that the shot was well tolerated, with no safety concerns.

The groups are preparing to file the vaccine with regulators. The data package will include data from the VAT02 booster trial, also released today. While the shot is clearly not perfect, another Covid jab that is easy to transport and store could make all the difference in efforts to get the whole world vaccinated.

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