A coronavirus vaccine being developed by Pfizer and German drug developer BioNTech spurred encouraging immune responses in several dozen healthy adults given the experimental shot in a small study, early data released Wednesday show.
The companies tested three different doses of their vaccine, which uses messenger RNA to train the body’s immune system against the SARS-CoV-2 virus. All 24 participants who received two injections of either the low or medium dose produced antibodies capable of neutralizing the virus at levels that were, on average, two to three times higher than what’s been observed in patients who’ve recovered from coronavirus infections.
Importantly, no serious side effects to vaccination were observed by study investigators. Most participants reported mild to moderate injection site pain and, after the second dose, tiredness, headaches and fever. A high dose wasn’t as well tolerated, however, and the 12 volunteers who received it were only given one dose.
The data are the first to emerge from Pfizer and BioNTech’s efforts to rapidly test several coronavirus vaccine prototypes, in hopes of selecting a candidate to take into a large global study later this month.
Results from the Phase 1 study suggest the companies’ technology works, although researchers still don’t know what kind of immune responses are needed to confer protection against coronavirus infection.
Convalescent sera, taken from the blood of recovered COVID-19 patients, serves as a kind of proxy. By comparing the immune responses of vaccinated individuals to antibody levels in convalescent sera, researchers hope to get a rough gauge of a vaccine’s potential.
On that measure, Pfizer and BioNTech’s candidate appears to have elicited as strong a response — or potentially an even stronger response — than Moderna’s front-running coronavirus vaccine. No specific data are yet available from Moderna and its U.S. government partners, however, making direct comparison impossible.
Both vaccines resulted in neutralizing antibodies “at or above” levels in convalescent sera, although Moderna only reported that data from eight volunteers versus the 36 participants from whom Pfizer and BioNTech obtained neutralizing antibody data.
Like Moderna, Pfizer and BioNTech are using mRNA, the genetic instructions cells use to make proteins, as the backbone of their vaccine. The technology has not resulted in an approved vaccine or drug, but it has enabled companies to move extraordinarily quickly in responding to the coronavirus pandemic.
Essentially, mRNA instructions for a key coronavirus protein, or part of it, are obtained and encased in what are called lipid nanoparticles — a fatty shield that allows the mRNA vaccine to get to cells without being destroyed in the blood.
Cells then use those mRNA instructions to produce the target protein, thereby teaching the body’s immune defenders to recognize it in the case of an actual infection.
Pfizer and BioNTech are developing four mRNA vaccine candidates, each a small tweak on the same general concept.
The candidate for which data are now available was tested in a Phase 1 study of 45 healthy adults, nine of whom received placebo. Twenty-four were given two shots, administered three weeks apart, of either a 10 microgram dose or a 30 microgram dose. The remaining 12 received one injection of a 100 microgram dose.
Those dozen study participants reported more side effects, with no greater immune response, leading the study investigators to drop plans for a second injection of the 100 microgram shot.
Pfizer and BioNTech plan to review the data, along with additional results being generated, to choose a dose — or potentially another variant of its mRNA candidate — to advance into a Phase 2b/3 study that could enroll as many as 30,000 people.
Moderna could also begin a Phase 3 study this month and other companies, like AstraZeneca and Sanofi, could be close behind.
The U.S. government is working with many of the leading companies, hoping to make a vaccine available to Americans in January 2021 — an aggressive and unprecedented timeline in vaccine development.
Pfizer CEO Albert Bourla has even said his company’s vaccine could be ready for emergency use by October.
In the event of successful development, Pfizer and BioNTech expect to be able to produce 100 million doses by the end of 2020, and potentially more than 1.2 billion doses by the end of next year.