Moderna’s highly-anticipated COVID-19 vaccine candidate has shown promise in a key early trial, producing antibodies in all partcipants tested.
The interim analysis of the phase 1 study of the candidate, mRNA-1273, evaluated a two-dose vaccination schedule of the shot given 28 days apart across three dosages – 25, 100, 250 µg – in 45 healthy adults aged 18-55 years. The initial results from participants who received both doses showed mRNA-1273 produced rapid and strong immune responses against SARS-CoV-2, the virus which causes COVID-19.
Despite producing a promising immune response in all patients, the vaccine also caused side effects, including mild to moderate fatigue, chills, headache and muscle pain.
In addition to those milder side effects, 40% of participants in the middle-dose group experienced a fever after the second vaccinations, with three of the 14 patients in the high-dose group experiencing severe side effects.
However, the high dose is no longer being used in the next, large-scale trials, with Moderna deciding that the prime dose level of 100µg will be used in later studies based on these early results.
Following two doses with the vaccine, neutralising antibodies levels among participants were similar to those seen in individuals who had tested positive and recovered from COVID-19. Although high levels of neutralising antibodies are not definitive proof that a vaccine is effective, they are still considered an important indicator of efficacy in early clinical trials.
The presence of such a promising immune response could signal that Moderna’s vaccine candidate will have the ability to protect against the virus later down the development line. Moderna will continue to evaluate the durability of the immune response in the phase 1 participants, who will be followed for one year after the second vaccination, with scheduled blood collections throughout that period.
The company has completed enrolment of two cohorts – healthy adults aged 18-55 years and older adults aged 55 years and above – in its phase 2 study of the vaccine. Study protocol for a phase 3 study has been also reviewed by the US Food and Drug Administration (FDA) and aligns with the agency’s recent guidance on clinical trial design for COVID-19 vaccine studies.
“This phase 1 data demonstrates that vaccination with mRNA-1273 elicits a robust immune response across all dose levels and clearly supports the choice of 100 µg in a prime and boost regimen as the optimal dose for the phase 3 study,” said Tal Zaks, chief medical officer of Moderna.
“We look forward to beginning our phase 3 study of mRNA-1273 this month to demonstrate our vaccine’s ability to significantly reduce the risk of COVID-19 disease.”
The clinical development of mRNA-1273 is being carried out in collaboration with the US National Institute of Allergy and Infectious Diseases (NIAID), with Moderna having previously been selected to take part in the US government’s ‘Operation Warp Speed’ initiative for the development of a successful COVID-19 vaccine.
Last week, reports emerged that clashes between Moderna and US government scientists over pivotal large-scale trials of the vaccine candidate were causing delays to the research, although it seems these concerns have been squashed given the timeline Moderna is still aiming for.
Even when taking into account the alleged discord, Moderna is still at the forefront of the race to find a successful vaccine, and was the first company to administer a COVID-19 vaccine candidate in human participants in March.