Vaccination with much-awaited COVID-19 vaccines has started in a number of countries, and other countries like Korea are expected to begin immunizing citizens within a couple of months. The successful development of vaccines in such a short period of time is an unprecedented scientific breakthrough. While highly promising, it is only the “end of the beginning”. There remain an equally challenging set of tasks around vaccine supply and vaccination, and a set of known unknowns create additional uncertainty.
The challenges ahead have one end in mind, reduction in the enormous burden of the COVID-19 pandemic. We still have to make 10-16 billion doses of high-quality vaccines, we have to prove that those vaccines protect and are safe for more than two months (the current data only cover 2 months), and we have to ensure global distribution and the vaccination of 5-8 billion people. The Coalition for Epidemic Preparedness Innovations, CEPI, estimated that it will be 2023-2024 before enough vaccine can be manufactured. Until those safe and efficacious vaccines can be deployed substantially, we will continue to see COVID infections, hospitalizations, and deaths. The world’s wealthiest nations have pre-ordered over 8 billion doses of vaccine, much more than needed. Modeling suggests that without some equity in vaccine distribution, global COVID deaths will double.
Despite a prodigious effort, many questions remain unanswered. As these relate to the COVID-19 vaccines, some of the known unknowns have already manifest in concern and confusion. At this point we know that the vaccines over a 2-3 month study period protection against COVID-19 disease and appear to be safe. There are still quite a number of things we don’t know. First, are we using the best possible dose and schedule? The UK is planning to vaccinate on a 3 month interval rather than the 3-4 week interval studied (all this without any data). The US is looking to reduce the dose of the Moderna vaccine. These changes in vaccine dose and schedule should be derived by clinical trial data, not empiricism. We also don’t know whether booster doses of vaccine will be necessary, or whether the booster can be a different vaccine from the original vaccination series. At this point, scientists are trying to understand how the current group of approved vaccines protected people. They are looking for a clue, called a correlate of protection, in the laboratory analysis of samples from people in the Phase III trials. Knowing the correlate of protection would make optimization easier, would speed the development of the next generation of vaccines, and would help us understand when to give booster doses.
An important unknown relates to how these new COVID-19 vaccines will impact spread in communities. The large Phase III trials are designed to answer a very specific question: does the vaccine protect individuals against COVID-19 disease. None of them answer the next two important questions: do these vaccines prevent infection or transmission? When asked what percentage of the population needs to be vaccinated we say, 60%, but this is an estimate. Is it 60% or will it be like measles vaccine (90~95%)? Practically this means that, for now, even after vaccination we should wear masks, and as before, masks will protect both the subject and the people around him/her if, despite vaccination, the wearer becomes infected. Effectiveness trials in large populations will help us to understand the impact of vaccination on communities, help us to understand herd immunity, and will give us confidence that these vaccines will have the anticipated impact on COVID-19 disease burden. Those trials need to be implemented as vaccination programs are starting, that is, now.
The vaccine is a weapon, a game-changing weapon, but to win the war against COVID-19 we need a strategy of prevention, critical logistical planning and an army of health care workers who will administer those vaccines to populations at risk. This will be a larger program than this year’s flu vaccination program (only a single jab for flu vaccines vs. two for COVID vaccines). With a limited supply of vaccines in the initial phase, high priority groups include the elderly and health care workers. Essential workers are the next layer. To some extent this will depend on the timing of vaccine supply. The recent MHRA of UK approval of the AstraZeneca vaccine could make it easier for other regulatory authorities, including Korean Ministry of Food and Drug Safety which recently started reviewing the dossier, to approve that vaccine for emergency use.
In addition, we expect to hear about other vaccines, from Novavax and Johnson and Johnson, in the next couple of months. Despite early delays Korea will gain access to safe and effective vaccines in the first few months of 2021. If experience with other vaccination campaigns is a guide, by the fall, more than 60% of Koreans should be vaccinated. Masks, distancing, and avoidance of crowds will need to continue even for people who have been vaccinated (since we don’t know if the vaccine prevents infection or transmission). We need to remain vigilant, and we have to keep the science focused on questions that will finally, practically bring this pandemic to a close.
Jerome H. Kim, MD, Director General, International Vaccine Institute
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