We are nearing the anticipated arrival of several vaccines which are hoped to contribute to our ability to control the COVID-19 pandemic. It is predicted that vaccines may begin to be available for distribution before the end of this year. Initial vaccine supply will be limited and will be prioritized to high-risk patients and front-line workers. It will take months to have sufficient supply for the entire adult population. A vaccination—if widely adopted—has the potential to help us achieve protection for enough of the population to decrease community spread and allow us to return to more normal levels of social and economic interaction. However, this will take time and require a substantial proportion of people to get vaccinated to be successful.
There are 4 stages of clinical trials in the development of any drug or vaccine. Phases 1 through 3 occur prior to approval and evaluate both safety and efficacy of the product. Phase 1 trials look at safety in healthy normal subjects. Phases 2 and 3 involve those with a disease or in the case of vaccines, a population at risk. Phase 2 trials are designed to look primarily at safety, but also evaluate efficacy. Phase 3 trials are larger and have the statistical strength to evaluate both safety and efficacy. Whereas early trials may evaluate tens or hundreds of patients, Phase 3 trials typically involve thousands of patients. In the case of the COVID-19 vaccines which are nearing approval, tens of thousands of subjects have been studied.
There are multiple vaccines in development using a wide range of technologies. The front-runners from Pfizer and Moderna use m-RNA technology to achieve an immune response. RNA vaccines are a new approach but have been studied for over a decade and have been tested both for infections and cancer therapy. They work by sending instructions to cells to manufacture a specific protein to which the immune system then creates antibodies. This newly created protein is not infectious and cannot cause the recipient to develop COVID-19. The vaccine does not enter the cell nucleus or interact with DNA. These vaccines have the advantage of being able to be quickly manufactured in large quantities.
Both RNA vaccines have already been tested in tens of thousands of people and initial safety information is very good. They both require two doses. For the Pfizer vaccine, doses are taken three weeks apart, whereas the Moderna vaccine requires 28 days spacing. As is common with most vaccines, there is the potential for some recipients to develop mild and temporary side effects, in this case a fever and muscle aches, particularly with the second vaccine dose. We don't yet know if the vaccines prevent viral transmission which is key to stopping the spread of COVID-19. We also are not yet aware of how long the immunity induced by these vaccines last. In addition, the vaccines require cold storage and in the case of the Pfizer vaccine this includes storage at -70 degrees Celsius which may cause logistics issues with distribution and storage.
The other leading vaccines in development use viral vectors to induce an immune response. Viral vector vaccines use weakened common viruses to deliver genetic material from the virus that causes COVID-19 to the person being vaccinated to induce an immune response. These are more difficult to manufacture than the RNA vaccines and if the recipient has immunity to the virus used as a vector, they may be less effective. Multiple other vaccines are in earlier stages of development that use more traditional inactivated virus technology. These vaccines have the advantage of using established technology, but the disadvantage of being slower to manufacture and in general inducing a lower immune response requiring multiple doses.
Vaccinations, even when available, are not an immediate cure for the COVID-19 pandemic. Much more data regarding long-term efficacy, data in specific at-risk populations, and further safety information regarding the vaccines will be forthcoming. Epidemiologists estimate it will require up to 70% or 80% of the population to either be vaccinated or have had COVID-19 infection—and for that immunity to be a lasting effect—before we achieve herd immunity and control of the virus. Strong and clear public health messaging on the need for vaccination once vaccines are available is paramount and the American Lung Association with its partners are asking Americans to begin having conversations about the vaccine now. Having a small proportion of the population vaccinated will not allow us to return to normal. There is still much to learn about the vaccines, including the long-term and even short-term vaccine effectiveness, or if the virus can be spread by vaccinated individuals. Given this, even after a safe and effective vaccine is available, it is critical for all Americans to continue to follow public health guidance, such as wearing a mask, physically distancing and washing hands. Scientific research, such as that being funded by the American Lung Association's COVID-19 Action Initiative will allow us to continue to make progress and control this pandemic, but it will take more time.
Until that time please stay home and stay safe.
Blog last updated: December 16, 2020