A peer-reviewed, first phase of Covid-19 vaccine testing is prompting calls for further research, but some are concerned over its side effects.
An experimental vaccine for SARS-CoV2 (the novel coronavirus) developed by the US biotech firm Moderna was deemed to be “generally safe” and provoked an immune response in the first phase of a study published to The New England Journal of Medicine.
The prototype vaccine, dubbed mRNA-1273, was tested in a small sample size of 45 healthy volunteers – aged from 18 to 55 – and showed it produced antibodies in response to the virus across three dose levels of 25, 100 and 250 micrograms.
The age range of this first phase of study is considered a limitation, in addition to its small sample size. Results on the second cohort of this phase, which included older people, have not yet published. Moderna said that given the effects of Covid-19 on older and elderly adults, additional evidence for the potential of a vaccine for this population is an “urgent priority”.
Moving on to further testing
Moderna said that the vaccine was “generally safe and well tolerated” after a two-dose vaccination schedule that occurred 28 days apart. Last month, the company said that it was to go with the 100-microgram dose for its late-stage study in the hope of minimising side effects.
Following the first dose, antibodies generated were shown to bind to the coronavirus, but they did not produce antibodies capable of countering its effects. However, of the 42 patients who received the second dose, all generated antibodies that were found to neutralise the virus.
During the final-stage trial, researchers will compare the vaccine with a placebo in 30,000 healthy subjects who are at risk of contracting the virus.
In testing, the most worrying side effects were seen in those given the 250-microgram dose, with three of the 14 participants reporting severe events. Side effects were most common during the second dose of the experimental vaccine, with all 15 participants reporting them in the 100-microgram group.
Most common side effects
Side effects in this group included fatigue (80pc), chills (80pc), headache (60pc) and myalgia (53pc). All participants reported pain at the injection site that was said to be either mild or moderate in severity.
“These phase-one data demonstrate that vaccination with mRNA-1273 elicits a robust immune response across all dose levels and clearly support the choice of 100 micrograms in a prime and boost regimen as the optimal dose for the phase-three study,” said Dr Tal Zaks, chief medical officer at Moderna.
“We look forward to beginning our phase-three study of mRNA-1273 this month to demonstrate our vaccine’s ability to significantly reduce the risk of Covid-19 disease.”
Speaking with Bloomberg, the director of the US National Institute of Allergy and Infectious Diseases, Anthony Fauci, said the data was “really quite promising”.
Tony Moody, a doctor and researcher at the Duke Human Vaccine Institute, cautioned that there were “a lot of adverse events”, which was “unusual”. However, Moody said the level of antibodies produced were “really encouraging”.