The French drugmaker has corrected the formulation of the shot, which was weaker than planned in the previous trial and failed to create enough of an immune response in people 50 years and older, according to a statement Monday.

Assuming results are good for the new second-phase trial — which will include 720 adults in the U.S., Honduras and Panama — the candidate could move on to late-stage studies in the second quarter and become available by the end of the year. The current trial will evaluate three different dosages for the vaccine, which requires two shots.

As two of the world’s biggest vaccine makers, Sanofi and Glaxo have faced heavy criticism for failing to lead the way on inoculating against the coronavirus — putting them in stark contrast to the likes of biotechs BioNTech SE and Moderna Inc., which developed highly effective shots in less than a year.

Separately, Sanofi also said it has agreed to make a plant in France available to Johnson & Johnson for the formulation and filling of about 12 million doses a month of that company’s Covid shot, assuming it gains regulatory clearance. The drugmaker already has a pact with Pfizer and BioNTech in which it agreed to perform some of the final steps needed to produce more than 125 million doses of that vaccine.

The one-dose vaccine from J&J is already being reviewed for emergency clearance in the U.S., and it could gain approval in Europe within the next few weeks, German Health Minister Jens Spahn said on Saturday. Meanwhile, regulators in the U.S. and U.K. are already reviewing data for a shot from Novavax Inc.

Glaxo shares erased their decline and rose as much as 0.5% in London. Sanofi was little changed in Paris.

Sanofi has insisted that it’s moving as fast as possible with its own candidate, which could provide countries with another powerful tool that can be more easily shipped and stored than some shots that must be kept frozen.

Sanofi’s shot combines the recombinant DNA technology it uses to make influenza shots with Glaxo’s immune-system boosting adjuvants. It’s most comparable to the vaccine from Novavax, which has been shown to be 89.3% effective in preventing symptomatic Covid-19 in a final-stage study. That shot, however, appears to lose protective power against a virus strain first identified in South Africa.

Despite the dosing problems in the previous trial, the Sanofi-Glaxo shot induced an immune response in younger people comparable to those who have recovered from Covid-19.

Sanofi said it has also begun development work against new variants of the virus that have emerged, which will be used in the next stages of its program with Glaxo.

The vaccine itself mimics the spike protein that the coronavirus uses to enter cells. That’s in contrast to many of the new vaccines that induce human cells to make the viral proteins.

Sanofi is also collaborating on a messenger-RNA Covid shot with Massachusetts-based Translate Bio Inc. That shot, based on similar technology as those of BioNTech-Pfizer, Moderna and CureVac NV, will probably enter early stage trials in March and could be approved by year-end, the company has said.