In the coming months, millions of Americans will have a decision to make — whether to get a COVID-19 vaccine. We as clinicians have an obligation to help patients make an informed choice. While a vaccine is not currently available to most people as manufacturing ramps up and the United States Advisory Committee on Immunization Practices (ACIP) determines an allocation schedule, phased deployment will occur over the next several months. Because so many people will have to make this important healthcare decision, the DynaMed Shared Decisions team at EBSCO developed a decision aid to assist in having this important discussion with your patients.
This decision aid answers some of the most frequently asked questions about COVID-19 vaccines and will evolve as the information does. As of the time of publication, the Food and Drug Administration (FDA) has authorized two vaccines for emergency use — one from Pfizer-BioNTech and the other from Moderna. Both are messenger RNA (mRNA) vaccines that carry instructions for cells to make the SARS-CoV-2 spike protein, which induce antibody and T cell responses.
Both vaccines were about 95 percent effective in large, placebo-controlled phase 3 trials, though this is likely to be higher than real-world effectiveness. Trials typically use a metric called vaccine efficacy (VE) to assess how well a vaccine works against the disease of interest. Vaccine efficacy is a relative measure that conveys how much less likely the disease is with the vaccine. It does this by comparing the incidence of disease in the vaccinated group with the incidence in the unvaccinated group. For instance, if two percent of people in the vaccinated group get the disease and 40 percent of people in the unvaccinated group get the disease, VE = 1 – (0.02/0.40) = 0.95 = 95%. This is just a simple example to demonstrate the concept using hypothetical numbers and the relative risk as the effect estimate. It is worth noting that vaccine efficacy can also be assessed with other relative effect estimates (e.g. the incidence rate ratio), but the central concepts behind the calculation remain the same. For simplicity, people often substitute the term effective or effectiveness for efficacy or efficaciousness when communicating trial results to the public or patients. This is ultimately of little consequence if we remember these are technically not the same thing. In terms of the vaccines, although a vaccine efficacy of 95 percent is encouraging, this is likely a ‘best-case scenario’ estimate. For instance, the highly controlled nature of trials and possible differences in people who volunteer for vaccine trials (e.g. healthy participant bias) both likely contribute to — among other things — higher adherence in the vaccinated group than will be seen in the real world. As a result, the real-world effectiveness of the vaccine will likely be lower than 95 percent. This problem is not especially unique to vaccines. The central concept we grapple with when gauging efficacy versus effectiveness falls under the domain of generalizability — that is, how well findings from a trial translate to the ‘messy’ real world.
Today, the decision aid does not include comparison between the vaccines because there is no direct comparative data and it is not clear if or when individuals will have their choice of vaccine. As already noted, the vaccines also fared similarly in terms of their efficacy. There have also been questions about contraindications, though there are limited data to inform who should not be vaccinated. People with history of serious allergic reaction (i.e. anaphylaxis) to a previous dose or any vaccine component should not be vaccinated, but it is unclear whether it poses a risk in others with severe allergies. The only contraindication noted by the FDA is serious allergic reaction to the vaccine or any of its components. While anaphylaxis is rare, appropriate medical treatment should be available to manage immediate allergic reactions. There is also limited information about the vaccine in people who are pregnant, breastfeeding, or immunocompromised, though none of these situations should be taken as an absolute contraindication.
Shared decision making is a collaborative conversation in which clinicians help patients reach evidence-based and value-compatible healthcare decisions. Carefully weighing medical history, risks of exposure and progression, and patient preferences with this decision aid in hand will support these important discussions with your patients.
