Shares of AstraZeneca’s American depositary receipt (ticker: AZN) climbed 7.5% on July 15 and 6.4% on July 17 on reports claiming that the data would be positive.
Yet the publication of the paper didn’t lift AstraZeneca’s stock. Shares of AstraZeneca’s ADR dropped 3% when the paper was released, before recovering slightly. By 11 a.m. Eastern, the stock was down 2.1% for the day, trading at $59.82.
“The immune responses observed following vaccination are in line with what we expect will be associated with protection against the SARS-CoV-2 virus, although we must continue with our rigorous clinical trial programme to confirm this,” the chief investigator of the Oxford Vaccine Trial and co-author of the study, Andrew Pollard, said in a statement.
In a press release distributed the same time that the Lancet paper was released, AstraZeneca noted that the vaccine induced T-cell responses in all participants, peaking at two weeks and lasting for two months. Neutralizing antibodies were present in 91% of patients after a month, and in all of the 10 patients who received two doses of the vaccine. In both cases, the levels of antibodies were in the same range as seen in patients who had recovered from Covid-19 infections.
The neutralizing antibody response may not have been enough to impress investors. Though comparing across studies is challenging, given differing methods, ways of measuring neutralizing antibodies, and sets of recovered Covid-19 patients to provide a baseline, other Covid-19 developers have claimed higher relative levels of neutralizing antibodies. Moderna (MRNA), for example, has said that its vaccine after two doses elicited levels of neutralizing antibodies that were four times higher than in a small group of patients who had recovered from Covid-19 infections.
Adverse reactions to the vaccine were minimal. “The majority of adverse events reported were mild or moderate in severity, and all were self-limiting,” the paper in The Lancet reported. The majority of patients who received the vaccine reported fatigue. Others reported muscle ache, chills, and feeling feverish. The severity of the reaction was highest a day after the injection.
The vaccine “was safe, tolerated, and immunogenic, while reactogenicity was reduced with paracetamol,” the paper concluded. “A single dose elicited both humoral and cellular responses against SARS-CoV-2, with a booster immunisation augmenting neutralising antibody titres. The preliminary results of this first-in-human clinical trial supported clinical development progression into ongoing phase 2 and 3 trials.”
Phase II/III trials of the vaccine are already ongoing in Brazil, South Africa, and the United Kingdom. The U.S. government vaccine effort, Operation Warp Speed, has said it aims for the AstraZeneca vaccine to be ready for distribution by October.
Also on Monday, Pfizer (PFE) and BioNTech (BNTX) announced a deal to supply 30 million doses of their Covid-19 vaccine to the U.K., and unveiled promising data on a Phase I/II trial of the vaccine in Germany.
Write to Josh Nathan-Kazis at firstname.lastname@example.org