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How effective Nanocovax vaccine would be?

By Nguyen Vu

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To assess the effectiveness of the locally produced Nanocovax vaccine against the coronavirus, it needs first to look at what the world normally calculates the prevention efficiency of a vaccine.

When Pfizer announced that its Covid-19 vaccine was 95% effective against the coronavirus at the end of last year, it did not mean that of all the volunteers taking part in the clinical trials, 5% of them contracted the disease and 95% did not. No, it isn’t! The ratio of infections in the trials was way lower, at 0.04%. The 95% prevention efficiency rate means a vaccinated person has an infection ratio 95% lower than non-vaccinated ones.

In phase 3 trials, Pfizer recruited 43,661 volunteers who were divided into two groups. The 21,830 people in group one were given the real vaccine and the 21,830 people in the other group, called the control group, were given placebos. Of course, none of the volunteers knew which group they belonged to. After several months, Pfizer recorded only eight infections in the first group while there were 162 cases in the control group. Therefore, the infection rate in the first group was 0.04% compared with 0.74% in the control group. In other words, the vaccine had reduced the risk of infection by 0.7 percentage point. The prevention efficiency was calculated using the formula in which 0.7% was divided by 0.74%, then multiplied by 100; that was 94.59% and rounded to 95%.

That means to identify the prevention efficiency of a vaccine in trial, it must undergo three phases on a considerable number of volunteers, of whom half are given a real shot while the rest given placebos. It takes some time to reach a certain ratio of infections in both groups. In case of Pfizer’s trials, the needed infections should be 164 cases. Prior to that point in time, when the trials reach the 94-case level, Pfizer estimated it roughly and announced the prevention efficiency of over 90%.

Nanocovax, a local vaccine developed by Nanogen, is now in phase 3b. Two doses [both the real vaccine and placebos] were to be administered to each of 13,000 people—an attempt to be finished by August 15. Of course, a report on phase 3 is not available now and of course, a prevention efficiency rate cannot be announced as per international practices. What has been reported to the National Research Ethics Committee is the results of the two trials in phases 1 and 2 (mid-term evaluation). Phase 1 trials are often to identify the safety of the vaccine in question and at the same time its optimal dose. Phase 2 means to assess whether the vaccine can create the immune response in administered people and to record side effects.

The National Research Ethics Committee said, “Nanocovax is safe and able to elicit the immune response,” which is rather optimistic. The committee has not yet appraised the vaccine’s prevention efficiency.

So, the next steps in line with international practices would put the massive use of the Nanocovax vaccine on hold for several months or even five or six months more so that the people with two jabs and placebos (13,000 in total) can have a certain number of infections. Then the prevention efficiency can be assessed upon which the Ministry of Health can license the use of this vaccine.

However, in the current urgent context of imported vaccines, it is not acceptable to wait for yet another long time. The best approach is arguably to consider Nanocovax a common national project so that everybody can roll up sleeves to step up its work progress. The Ministry of Health should have two separated divisions. The first responsible for approving vaccines will objectively study results and exercise certain caution. Yet the support division should spare no efforts to help Nanogen carry out the next steps, including costs, personnel and other resources.

Some research studies have concluded that a Covid-19 vaccine can be ratified relying on the production of antibodies and does not need to fulfill the phase 3 trials because antibody production is a strong indicator for the success or failure of a vaccine. Take for example, the research of Oxford Vaccine Group in cooperation with Britain’s National Health Service and AstraZeneca, or the research conducted by New South Wales University in Australia. These research projects maintain that the immune response (producing neutralizing antibodies) of a person given a Covid-19 vaccine can be employed to assess the prevention efficiency of the vaccine. To be more specific, Australian researchers used data from seven vaccines with measured volume of Y protein, which relates to neutralizing antibodies produced by a person after being infected with Covid-19 or being administered a Covid-19 vaccine. Utilizing the statistical analysis method, the researchers determined the relationship between the immune response and prevention efficiency so as to calculate the clinical effects of these vaccines.

Researchers have argued that it is not difficult to count the number of antibodies in a human body. It is much easier and quicker than traditional methods. They therefore concluded that in the future, this method could be employed to ratify vaccines used in emergency cases to shorten time.

Whether Vietnam should make use of the above research results for Nanocovax should be the jobs of local researchers and the authorities concerned. However, this shows that a new orientation has been seen and can be put into use in the current urgent context. Of course, some other conditions must be met to minimize risks. For instance, vaccines approved this way can be used for a certain class of people, those under 45 or those in the hotspots of the pandemic.

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