Assistant Director of the Pan American Health Organization (PAHO), Dr Jarbas Barbosa, says an approved coronavirus (COVID-19) vaccine could be available for distribution and administration during the first half of 2021.
Speaking during PAHO’s COVID-19 digital briefing on Thursday, Barbosa said this projection is based on the progress of Phase III clinical trials involving 10 vaccine candidates, and the anticipated timeline for the conclusion of engagements in this stage by the producers.
Stage three of the clinical trial process entails large-scale expansion of tests to thousands of volunteers, with some receiving placebos to analyse for safety, dosage and efficacy, as well as side effects in a larger population.
Barbosa advised that concluding engagements for the 10 candidates are expected to span the remainder of 2020 into early 2021.
He noted, however, that other potential factors, such as the suspension of a vaccine’s administration during clinical trials due to safety concerns or to identify a larger number of volunteers could figure in the process and impact the targeted readiness timeline.
“Once Phase III trials come to an end, the results need to be presented to the World Health Organization (WHO), and a file has to be prepared to request registration. The expectation, however, is that we could have a vaccine available for use in the first half of 2021… [that is] our best estimate,” he added.
According to the WHO website, up to Thursday, November 5, there were 154 COVID-19 vaccine candidates in the preclinical evaluation phase, 32 in the Phase I clinical trial stage, 13 in Phase II, along with 10 in Phase III, and five that are being used on a limited basis. None, however, has been approved for wide-scale distribution.
The standard vaccine testing procedures are – Phase I: small-scale safety trials – tests on a small number of people for safety, dosage, and efficacy; Phase II: expanded safety trials – tests expanded to hundreds of people; and Phase III: large-scale trials – tests expanded to thousands of people, with some receiving a placebo, to test for safety, dosage, and efficacy as well as side-effects in a larger population.
The procedures also entail approval by some countries for limited use of vaccines without the results of Phase III trials.
Barbosa said PAHO does not anticipate any risk of side effects in individuals who are inoculated with a vaccine approved by member countries’ national regulatory authorities and recommended by the WHO.
He pointed out that the WHO has a Prequalification Team that will review all COVID-19 vaccines that will be processed via the entity’s COVID-19 Vaccine Global Access (COVAX) Facility for distribution to member countries.
The Facility is designed to accelerate equitable access by countries globally to appropriate, safe and efficacious vaccines.
Additionally, Barbosa said vaccines will be assessed by national regulatory authorities.
He also emphasised the need for countries to institute a post-marketing vaccine surveillance system to track the outcomes of the vaccine administration process.
Barbosa said the entity is working with the member countries to develop this mechanism in preparation for their receipt and administration of COVID-19 vaccines.
“We expect that these vaccines will be safe, as all the other vaccines that we use; and strengthening the post-marketing surveillance is another critical step in the process. We call this ‘Phase IV clinical trial’, because [it focuses on emerging empirical] data when the vaccine is being used,” he added.