Despite hopeful buzz on COVID cures, this vaccine specialist says these are the challenges ahead
Assuming all these vaccine candidates successfully pass the Phase 3 trials, what happens next? DR. MELVIN SANICAS
ANCX | Jul 22 2020
The global COVID-19 cases total is almost 15 million with over 613,000 deaths and over 8,900,000 recoveries, according to the World Health Organization COVID-19 dashboard. COVID-19 is now under control in many countries. The value of R0 (R naught or R zero) – average number of people infected by someone with the disease – was over 3 when the pandemic started. To control the outbreak, R0 should be less than 1 so infection will spread slowly and eventually die out. Now it is down below 1 in many countries, unfortunately not in the Philippines.
However, there are reasons to be hopeful. Last week, Moderna reported that their mRNA vaccine candidate, developed with support from the US National Institute of Allergy and Infectious Diseases, generated immune response and was generally safe.
The Oxford vaccine, supported by AstraZeneca expresses the SARS-CoV-2 spike protein, used by the coronavirus to invade human cells. (Expression here refers to the production of the proteins by cells.) Researchers conducted the 1st and 2nd phase trial in 1,077 healthy adults ages 18 to 55 in the United Kingdom. Those in the control group received a licensed meningitis vaccine and the investigators followed up the participants for 2 months after vaccination. The vaccine induced strong antibody and T-cell immune responses, which were even higher in the group that was given a booster (extra administration of a vaccine after an earlier / prime dose). Antibody responses were found in 32 of 35 participants at day 28 and all subjects who got the booster dose had antibody responses. When compared to the control group (given the meningitis vaccine), the SARS-CoV-2 vaccine group experienced minor side effects. No serious adverse events occurred, and taking paracetamol / acetaminophen did not affect the immune response from the vaccine.
The vaccine, developed by CanSino Biologics, enrolled 508 healthy adults between 18 and 80 years old in Wuhan, China. Researchers tested two different doses against placebo and followed up participants for 28 days. There were no serious adverse events and minor ones were more frequent in those given the COVID-19 vaccine. The vaccine also produced neutralizing antibodies and over 90% of the recipients showed T-cell responses. People older than 55 years old and those who had earlier exposure to adenovirus (the vector used in the vaccine) had somewhat lower humoral responses, but the T-cell response was not affected.
Biotech firm BioNTech and Pfizer also reported additional data from their experimental COVID-19 vaccinethat showed it was safe and induced an immune response in patients. The data is available on an online preprint server at MedRxiv and is undergoing scientific peer-review.
These results are optimistic because they mean that these vaccine candidates can move on to Phase 3 efficacy studies – where they will be given to more people, usually over 10,000 for vaccine studies. The reduction of disease in the vaccinated group will be compared to the unvaccinated group so researchers can calculate the vaccine efficacy. The published results from the different vaccine candidates are broadly similar and promising, despite differences in the vaccine technology used and the country where the studies were performed. The safety data from Moderna, Oxford, and CanSino are reassuring but there is still a long way to go.
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Assuming all these vaccine candidates successfully pass the Phase 3 trials, what happens next? Firstly, the manufacturers need to develop a way of producing the vaccine on a huge scale. Secondly, medicines regulatory agencies (such as the US Food & Drug Administration, European Medicines Agency, UK Medicines and Healthcare products Regulatory Agency, or our own Philippine FDA) must review all data and approve the vaccine. Thirdly, there will be a big logistical challenge of actually vaccinating people. Some countries have already started drafting agreements with the vaccine manufacturers for millions of doses to be delivered once the vaccine gets licensed. Are we one of those countries?
On the day the first COVID-19 vaccine is finally approved, I will be celebrating like never before. Then I will continue to wash my hands, wear a mask outside the house and maintain physical distance with everyone. Why? Because I know that when a vaccine is officially approved anywhere in the world, there won’t be enough available for the 7.8 billion people on the planet.
Dr. Melvin Sanicas (@Vaccinologist) is a public health physician specializing in vaccines and infectious diseases.
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