By Christine M. Akamine ’15 and Michael B. Ing ’90
Background and Vaccine Efficacy
The Coronavirus Disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has had a devastating impact globally since its emergence in December 2019. Vaccines are the most promising component of the effort to reduce COVID-19 associated morbidity and mortality. In response, numerous vaccine candidates have been developed and are in various stages of evaluation (see Table 1). In December 2020, two vaccines were granted emergency use authorization (EUA) by the US Food and Drug Administration (FDA) for the prevention of symptomatic COVID-19, the BNT162B2 (Pfizer-BioNTech) and mRNA1273 (Moderna) vaccines. Both vaccines are mRNA-based and encode the full-length spike protein of SARS-CoV-2. These vaccines have demonstrated that they are highly efficacious for the prevention of symptomatic COVID-19 disease starting 14 days after the second dose of vaccine. Pfizer-BioNTech reported 95% efficacy and Moderna reported 94% efficacy. All available COVID-19 vaccines have undergone rigorous testing in large clinical trials to ensure they meet strict safety criteria. Additionally, the scientific methods and full data sets were extensively peer-reviewed by multiple groups including the Centers for Disease Control (CDC), US FDA, and the Advisory Committee on Immunization Practices (ACIP). These data have since been published and are available to the public. Given the limitation in available vaccines, the ACIP has published recommendations regarding the COVID-19 vaccine prioritization and allocation (see Table 2). All adults in the United States will be eligible for the vaccine after April 19, 2021.
Potential Benefits and Precautions
No vaccine is 100% effective. However, we do know that these COVID-19 vaccines have been extremely effective in the prevention of severe COVID-19 disease with virtually no reported COVID-19-related deaths following vaccination. There is also recent data indicating that vaccinated persons who develop symptomatic infection shed significantly less virus in their nasopharyngeal tissues. This explains why vaccination prevents severe disease and also indicates that infection following vaccination will likely result in less person-to-person transmission. Since it is still unknown whether vaccinated persons with asymptomatic infection are still infectious, even vaccinated individuals should wear masks and practice social distancing to avoid the potential propagation of the virus and further spread of disease to others.
Since it is still unclear whether all previous COVID-19 infected persons have adequate immunity, vaccination is still recommended following COVID-19 infection. Those developing symptomatic infection after the first dose of the vaccine should also receive their scheduled second dose after their infection has resolved. It is not yet known if the current COVID-19 vaccines will be effective against all of the new emerging COVID-19 variants. However, since the goal is to halt transmission of the virus and eliminate viral replication, vaccination is critical in decreasing the opportunities for the virus to mutate into variant strains.
Side effects after vaccination are common and most are mild to moderate in severity. Fatigue, headache, myalgia, fever, and injection site reactions are common. Reactogenicity is greater in the younger population and after the second vaccine. Having prior infection with SARS-CoV-2 did not result in greater reactogenicity. Anaphylaxis is extremely rare after vaccination with 11.1 cases per million doses after the Pfizer-BioNTech COVID-19 vaccine and 2.5 cases per million doses after the Moderna COVID-19 vaccine. Those receiving the vaccine should follow the CDC’s recommendations for post-vaccination observation to monitor for signs and symptoms of anaphylaxis so that treatment can be delivered promptly.
In conclusion, COVID-19 vaccines are effective, safe, and are pivotal in our fight to curb this pandemic. They are extremely effective in preventing symptomatic COVID-19 infection and death. Severe side effects are extremely rare. We owe it to ourselves, our families, and society in general to get vaccinated, to prevent severe disease, transmission to others, and create the “herd immunity” necessary to bring this pandemic to an end.