The first of four experimental Covid-19 vaccines being tested by Pfizer and its German partner BioNTech showed encouraging results in initial trials with 45 people, the companies said today.
Volunteers in a study who received a low dose or median, in two injections within one month, had immune responses in the range considered protective when compared to some survivors of the disease, according to preliminary results.
Side effects were common for vaccines, such as injection site pain and fever.
The report was submitted for publication in a scientific journal, but has not been reviewed. With its other potential candidates still in the initial testing stage, Pfizer is looking to start a large-scale study this summer, but cannot say yet which injection it will include.
The researchers chose to apply low and medium doses. The higher-dose injections caused more reactions, with no visible added benefit.
About 15 vaccines for Covid-19 are in human trials worldwide and several plan to start large-scale studies to see if they really are effective.  Different companies are working on different types of vaccines, which increases the chances that at least one will work, although there are no guarantees. Pfizer and BioNTech candidates use part of the coronavirus genetic code to prepare the body to recognize and attack the virus.
This week, Inovio Pharmaceuticals said its gene-based candidate had encouraging results in a similar test with 40 volunteers.