As the human toll of COVID-19 continues in its catastrophic progression, the world is desperately waiting for a vaccine that could put an end to the pandemic. Researchers are considering all kinds of potential vaccines: live attenuated (pathogen weakened) vaccine, inactivated (killed) vaccine, vector-based vaccine, protein subunit vaccine, DNA vaccines, mRNA vaccines—all with their respective advantages and disadvantages. Even the BCG vaccine for TB is being considered for its possible benefits against COVID-19, although the World Health Organization (WHO) has warned against pinning hopes in it without the benefit of actual clinical trials.
As with pharmaceuticals, vaccine candidates go through pre-clinical (animal) testing first before they go through the three phases of clinical trials in humans. Not all vaccine candidates become successful (there are over 80 now for COVID-19) and the whole process requires time: one to two years for safety (Phase 1), two to three years to further demonstrate safety and some efficacy (Phase 2), and another five to 10 years for safety and efficacy in natural disease conditions (Phase 3). Regulators must continue to require vaccine developers to check for potentially harmful responses in animal studies. They must also carefully assess the volunteers for the presence of antibodies against any coronaviruses before enrolling them in safety trials.
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We hear experts saying it will take 18 months to develop, test, approve, and manufacture a vaccine. Doubtless, many would feel that this is far too long, but even then, it will be a record-breaking achievement. The poliovirus was discovered in 1908 but the inactivated polio vaccine (IPV) only became available in 1955 while the more convenient form, oral polio vaccine (OPV), became available in 1961. However, given the dire need and immense pressure to control the pandemic, a COVID-19 vaccine could be ready sooner, if scientists and regulatory agencies are willing to shorten the usual processes. Since its genetic sequence was released, at least seven candidate vaccines have reached the stage of clinical trials.
Capacity and capability
Apart from safety, efficacy, and quality, we need to make sure that work is being done in parallel to make sure we have the necessary manufacturing capacity to produce the millions or even billions of doses that will be needed. Production of a vaccine in a massive scale is extremely challenging because vaccines are biological products and as such are subject to widespread variation even between batches. Once a vaccine is licensed, there will still be the question of prioritization: who gets it first? Countries like the Philippines, who largely rely on importing vaccines or counting on international organizations like UNICEF, stand to lose unless the government takes action in ensuring vaccine manufacturing capacity and including it as a matter of national health security.
Meanwhile, we are learning more about the coronavirus. But there are still many unknowns, including how long a vaccine will confer protection. There have been anecdotal reports of re-infection. This is not well understood but this has important implications for vaccine development.
Despite these hurdles and caveats, a vaccine offers hope of a return to “normal,” which is why people—even former anti-vaxxers—are pinning their hopes on it. Even so, addressing the root causes of ‘vaccine hesitancy,’ including mistrust in our health institutions, is more vital than ever before—especially as the mishandling of the pandemic can aggravate these negative attitudes. As the dengue vaccine scandal in the Philippines shows, rushing vaccines could result to unwarranted setbacks and further aggravate anti-science sentiments.
Meanwhile, other pathogens (measles, polio) have not gone away and are preparing to make a grand comeback, with routine immunization programs suspended in many countries. While we wait for a COVID-19 vaccine, we must not allow those that already exist, and proven to work for other diseases, to go to waste. The pandemic reminds us that vaccines can save not just our old way of life, but billions of lives around the world.
Melvin Sanicas (@Vaccinologist) is a public health physician specializing in vaccines and infectious diseases. Gideon Lasco (@gideonlasco) is a health systems researcher and medical anthropologist.