Vaccine makers, including two of the biggest in the world, suffered setbacks in the push to get more Covid-19 shots across the line, tempering a run of positive news.
Sanofi and GlaxoSmithKline Plc delayed advanced trials of their experimental Covid-19 shot after it failed to produce a strong enough response in older people, pushing its potential availability to the end of next year. In another blow, trials of a vaccine being developed by CSL Ltd. and the University of Queensland in Australia ran into difficulties.
Sanofi and its U.K. partner will begin a new second-phase study with a more concentrated antigen in February after they said the current dosage failed to generate a good immune response in people 50 years and older. Younger adults showed a response similar to patients who have recovered from the disease.
The problem arose after two different reagents used to measure vaccine formulations provided inaccurate information about the concentration of antigens, Sanofi said in an emailed statement. The companies notified U.S. officials about the matter.
The delay underscores the difficulties and uncertainties companies face in developing shots in record time against a disease that’s already claimed more than 1.5 million lives. It’s also a blow for governments that were counting on supplies from the two vaccine giants amid expectations the world will need multiple inoculations to stop the spread of the pathogen.
Australia meanwhile canceled an order for 51 million doses of a Covid shot being developed by CSL and the Australian university. A component of the vaccine comes from the human immunodeficiency virus, and while that posed no risk of infection, some trial participants had false positive tests for HIV.
The announcements temper some of the optimism following positive trial results from Pfizer Inc. and Moderna Inc. Another inoculation from AstraZeneca Plc and the University of Oxford looks promising, too, despite questions about its effectiveness in older adults. The U.K. and Canada have already approved a shot from Pfizer and partner BioNTech SE that employs messenger RNA technology, and the U.S. and Europe may do so soon. China and Russia have already begun administering their own vaccinations.
Sanofi fell as much as 3.3% Friday in Paris, while Glaxo was little changed in London.
The delay to the Sanofi-GSK vaccine means it may not reach the market until the fourth quarter of 2021 rather than the middle of the year. A study using an improved antigen mix, exposing monkeys to the virus, showed a rapid clearance of the pathogen from the nose and lungs.
The companies are planning a new trial that could include a head-to-head comparison with an approved Covid-19 vaccine to speed research. The companies haven’t disclosed how many people will be included. Advanced-stage tests could start in the second quarter of next year.