COVID-19 Vaccine Update: Moderna vaccine initial test results hailed in media, but experts are skeptical
On May 18, Moderna Inc announced that the preliminary results from the phase 1 trials of their mRNA-based COVID-19 vaccine seem to be promising.
On May 18, the American biotech company Moderna Inc announced that the preliminary results from the phase 1 trials of their mRNA-based COVID-19 vaccine seem to be promising.
The research, being led by the National Institute of Allergy and Infectious Diseases (NIAID), USA, had started enrolling volunteers in March. As per Moderna, a total of 45 volunteers in the age group of 18 to 55 years were to be enrolled for the trial originally. The volunteers were to be divided into three different dose cohorts - 25 µg (microgram), 100 µg and 250 µg. The vaccine was to be given in two doses, 28 days apart.
According to the press release, Moderna recently collected immunogenicity (ability to generate an immune response) data for the 25 µg and 100 µg cohort (after two doses or day 43) and 250 µg cohort (after one dose or day 29). Four volunteers each from the two cohorts (total 8 volunteers) have reportedly shown the presence of neutralising antibodies in their blood equal to or above the amount present in the blood of convalescent patients (those who are recovering from the disease) of COVID-19.
However, since the full details of the trial haven’t been released so far and the NIAID hasn’t given any new statement about it, some experts are pointing out that no conclusions can be drawn until the full data is disclosed.
The Moderna vaccine
On Jan 13, Moderna Inc. and NIAID’s research team finalised the sequence of RNA-1273, their vaccine candidate. The Chinese authorities had released the nucleic acid sequence of the novel coronavirus on Jan 11.
RNA-1273 is a novel lipid nanoparticle (LNP)-encapsulated mRNA based vaccine. It encodes the spike protein of SARS-CoV-2, the causative agent of COVID-19. The spike protein is what the virus uses to bind to and enter the host’s healthy cells.
By Feb 24, Moderna had shipped the first batch of the vaccine to National Institutes of Health (NIH), US for the phase 1 clinical trials.
On March 16, the NIH announced that they have administered the vaccine to the first subject. This was a total of 63 days from selecting the sequence. The trial had begun at the Kaiser Permanente Washington Health Research Institute (KPWHRI) in Seattle. Though, the original trial only had 45 people in the age group of 18-55 years.
On April 17, NIH announced that they are going to add 6 more cohorts, 3 out of which would be in the age group of 56-70 years and the other three would include people above the age of 71 years. The enrollment of the later 6 cohorts is currently going on. Testing the vaccine on the older age group would help assess its effectiveness in the elderly, which is a high-risk group for the coronavirus infection.
The most common concerns that some experts reportedly have right now is the lack of data from Moderna. The information released so far is only for the first eight people from the trial and the amount of antibodies made in their body. Also, there is no saying how effective the vaccine is in the elderly yet (enrollment for that age group is ongoing) and how long the antibodies will stay for.
As per the press release by Moderna, they have only released the data they’ve received so far. All the participants in the three cohorts had reportedly shown the presence of antibodies by day 15 after a single dose. Binding antibodies (or non-neutralising antibodies) were seen in the 25 µg and 100 µg cohort. These type of antibodies are unable to prevent infection.
Though the data for neutralizing antibodies is only available for the first 8 people right now, in animal models, the vaccine had shown to suppress viral replication in the lungs. Neutralising antibodies are those that actually neutralize the virus and prevent infection.
Also, one participant in the 100 µg dose had a grade 3 erythema around the injection site and in the 250 µg cohort, 3 volunteers had grade 3 systemic symptoms after the second dose. All these events had been temporary and resolved on their own.
Based on the current data, Moderna and NIAID have decided to test the vaccine in the 50 µg dose and do the phase 2 trials only in the 50 µg and 100 µg cohorts only to find the right dose that is effective for pivotal studies.
For more information, read our article on Why is it taking so long to develop a COVID-19 vaccine
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