UPDATED: Valneva soars after its COVID-19 shot tops AstraZeneca's in head-to-head trial

The U.K. government has waited a long time for this news. So long, in fact, it canceled a contract for 100 million doses of the Valneva COVID-19 vaccine last month. (Valneva)

A month after the U.K. government canceled a contract for 100 million doses of its COVID-19 vaccine, Valneva says the jab was better than AstraZeneca's conditionally approved shot. 

In a phase 3 trial, Valneva's vaccine topped AstraZeneca's Vaxzevria by producing a higher mean level of neutralizing antibodies—the proteins responsible for preventing pathogens from spreading infection—against SARS-CoV-2, the virus that causes COVID-19. The Valneva recipients also saw fewer side effects, the company said.

The same number of COVID-19 cases cropped up in each patient group, and there were no severe cases, the company said

That's a massive boon for Valneva as the company's stock shot up nearly 35% to $37.83 a share as of 10:32 a.m. Eastern time. Valneva's stock cratered 42% when the U.K. government axed the vaccine contract last month. 

Ethics were core to Valneva’s decision to test against an approved product rather than the traditional route of comparing an investigational treatment to placebo, a Valneva spokesperson said via email. The company said using a placebo would not pass ethical muster at this stage in the COVID-19 vaccine rollout.

The U.K.'s regulatory body had agreed on that trial design, Valneva said. 

The company also had to restrict its comparisons to the AstraZeneca shot—in people over 30 years old rather than the entire study population—because the U.K. limited the use of Vaxzevria to that age group after noticing blood clot issues. That trial adjustment, with just one-fourth of the study comprising the control group, means efficacy estimates are harder to come by.

The vaccine is similar to that of most flu shots in that it uses the traditional technology of an inactivated virus. Valneva's vaccine is also made using the manufacturing technology behind its approved Japanese encephalitis shot, Ixiaro.

Valneva started the process of filing for initial approval with the U.K.’s regulatory body in August and now expects to finalize that next month, with a potential initial nod coming by year’s end. The company is also now preparing to start the conditional approval process in the European Union with the European Medicines Agency. More discussions have been initiated with countries and regulatory agencies in parts of Asia, Valneva said Monday.

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Valneva sees its candidate as a potential route to vaccination for those who haven't received a jab during the pandemic. 

"We are committed to bringing our differentiated vaccine candidate to licensure as quickly as possible and continue to believe that we will be able to make an important contribution to the global fight against the COVID-19 pandemic," CEO Thomas Lingelbach said in a statement.

The head-to-head phase 3 trial enrolled 4,012 people aged 18 years and older across 26 sites in the U.K. Nearly 3,000 people aged 30 and up got either the Valneva vaccine (1,977 people) or the AstraZeneca jab (995), both in two-dose regimens 28 days apart. Another 1,040 people under the age of 30 got the Valneva vaccine.

Patients 30 years and older who received the French company's shot reported fewer adverse events than those who received AstraZeneca's. Injection site reactions stood at 73.2% for Valneva's vaccine and 91.1% for AstraZeneca's, and 70.2% versus 91.1% for systemic reactions. 

RELATED: Valneva, hit by COVID contract chaos, sees Lyme disease vaccine drop-off in phase 2, but boosters helping

The fact that there were no cases of severe COVID-19 for either vaccine in the trial could be a sign the vaccines may prevent severe cases of the disease caused by the circulating variant, Valneva said. During the study, that variant was predominantly delta.

Adolescents are also testing the vaccine. About 660 patients, aged 12 to 17, are slated for that trial, Valneva said Sept. 23. A booster trial, in which an additional dose is given six months after initial vaccination, also began last month.

Valneva is testing the vaccine in New Zealand as well, with 306 people aged 56 and older enrolled in that study. The biopharma is preparing for trials in kids five to 12 years old. 

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The COVID-19 vaccine news comes after Valneva and partner Pfizer said their investigational Lyme disease jab will need a booster last month, with early data suggesting that an additional dose can help. 

Editor's note: This story was updated at 12:46 p.m. ET with information from a Valneva spokesperson.