Challenges for COVID-19 vaccines

At least 10 COVID-19 candidate vaccines have reached the phase of clinical trials

The global scientific and technological challenges for COVID-19 vaccine development
Vaccines must undergo several trials to prove they are safe and effecitve . Photo: File photo/EL UNIVERSAL
English 22/07/2020 15:38 Mexico City Actualizada 15:38

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The race to find a vaccine and stop the spread of COVID-19 is reaching a new level. According to Gavi, the Vaccine Alliance (GAVI), an international association of the public and private sectors that includes institutions like the World Health Organization (WHO), the World Bank, the UNICEF, the Bill and Melinda Gates Foundation, and others, several technologies are currently being tested to stop the pandemic. From the 133 candidate vaccines in which researchers all over the world are working on, 10 have reached the phase of clinical trials. The three vaccines with most progress are in charge of China’s CanSino Biologics, the Jenner Institute of the University of Oxford, and the Moderna laboratory in collaboration with the U.S. national health institutes.

Sara Gilbert, a member of the team that began working on the drug of the University of Oxford on early January, has said they chose as a vector for the vaccine a chimpanzee adenovirus (ChAdOxf) since it can generate a strong immune response in a single dose and is not a replicant virus. For the creators of the vaccine, this also makes it safer for children, elderly people, and people with underlying health conditions such as diabetes. The team saved time thanks to the previous experience of a vaccine created for another disease caused by a coronavirus, the Middle East Respiratory Syndrome (MERS).

According to reports of the University of Oxford, the chimpanzee adenoviral vectors have been used un thousands of individuals with ages that range from one week to 90 years old in vaccines aimed for over 10 diseases.

CanSino used a methodology that is quite similar to Oxford’s but its recombinant vaccine co.developed with the Beijing’s Institute of Biotechnology (BIB) uses as a vector a strain of the same respiratory virus that is found in human beings, a type 5 recombinant adenovirus (Ad5). The candidate vaccine is based on the technological platform with which a vaccine against ebola was developed.

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In the case of Moderna, the strategy is different: The vaccine consists of creating a copy of the genetic material; the RNA is injected in the human body and “orders” cells to produce a spike protein like the one of the virus to create immunity. The article “A strategic approach to COVID-19 vaccine R&D” published on the Science magazine, mentions that, precisely, one of the points against this vaccine is that it lacked the commercial experience of products created with other technological platforms. An RNA vaccine has never been approved for human use.

Vaccines for everyone?
Global access to a vaccine against COVID.19 is another of the main challenges. Alliances will be fundamental for the efforts to pay off. One of the examples of this works is given by the University of Oxford which, after joining the AstraZeneca laboratory a little over a month ago, consolidates a series of agreements so that its vaccine could also reach developing countries.

India has become the main exporter of generic drugs and vaccines in the world and India’s Serum Institute (SSI), a producer of immunobiological drugs, will be fundamental in massive production. With a history of over half a century, this company produces and sells to 165 countries the highest number of vaccines in the world; every year, it makes over 1 billion doses of 20 different vaccines that are made in a plant of 8,000 workers with facilities distributed throughout Europe.

According to information from the University of Oxford, the plan is for the SSI to obtain a license to provide 1 billion doses for low and medium-income countries with the commitment of providing 400 million before the end of 2020. They have also reached an agreement with the Coalition for Epidemic Preparedness Innovations (CEPI) and the GAVI to support the production, purchase, and distribution of 300 million doses of the vaccine, should it be safe and effective.

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Phases and challenges
Generally, during Phase I, vaccines test dose levels in groups of up to 100 people and aim to establish they do not pose a threat to health. Phase II is a bigger-scale study that involves hundreds of people to evaluate the common secondary effects in the short term. It can even show the variations of the immune system in some age ranges.

Phase III recruits thousands of volunteers and the response of those who received the vaccine is compared against those who did not. This test collects statistical data and is used as a new opportunity to identify other secondary effects that had not been registered in the previous phases. The vaccine developed by the University of Oxford is currently at a transition phase of the clinical trials of phases II and III that involve nearly 10,260 people from Great Britain, including children and elderly people.

Andrew Pollard, chief of Oxford’s Vaccine Group, has stated in information provided by the Jenner Institute, that the clinical tests have progressed very well and now, they are at the stage to monitor how the vaccine induces immune responses in elderly people and to evaluate if it can protect a wider population. On the other hand, Moderna also announced on July 19 that it would begin phase III. Nevertheless, they are aware that a significant proportion of the vaccines tested in clinical trials does not work. If it is not feasible to show that the vaccine protects against the virus, the progress would need to be checked and alternative approaches should be examined, such as the use of different dose levels.

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Vaccines are analyzed in places with active outbreaks, for the trials depend on healthy volunteers being exposed to the virus to prove the vaccine actually works. If the transmission is still high, there will be enough data in a couple of months, but if transmission levels slow down, this could triple the waiting time for the results.

In order to evaluate if the vaccine works to provide protection against COVID-19, the number of infections in a control group is compared to the number of infections in a vaccine group. They must recruit those who have a higher chance of being exposed to SARS-CoV-2, such as healthcare workers, but the decrease of cases in many places that are about to begin the trials has also become a paradox to find a fast solution against the pandemic.

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