COVID-19 UPDATE
COVID-19 in 2021: Vaccine Progress and Challenges By Jan E. Patterson, MD, MS, MACP
Just a year ago, we were headed into a summer surge of COVID-19 hospitalizations and deaths. As we cared for sick patients and saw continued increases in hospitalizations and deaths, we worked to increase testing, improve public health measures and discover what therapies worked best. We could hardly envision that an even worse winter surge was coming, in which we would exceed 500,000 U.S. deaths from COVID-19. It was also hard to imagine that by the year’s end, we would have effective vaccines against COVID-19, but vaccination of health care workers began in December. Even better, the vaccines were more efficacious than we could have imagined. In clinical studies, mRNA vaccines (Pfizer/BioNTech, Moderna) were 94-95% effective against symptomatic disease and even more effective against hospitalizations and death. Real-world data after the FDA Emergency Use Authorization (EUA) has confirmed 94% effectiveness against symptomatic disease of the mRNA vaccines after two doses in health care workers, and efficacy in the general population appears to be similar. The single dose, replication-deficient adenovirus vector Johnson & Johnson/Janssen ( J&J) vaccine was 66% effective against COVID infection in clinical studies. Most real-world efficacy data is for the mRNA vaccines, and real-world data on the J&J vaccine is still being evaluated. Evidence is also accumulating that each of the FDA-authorized vaccines provide significant protection against asymptomatic infection. For all of these vaccines, the most protection was achieved two weeks after the final vaccination dose. Effectiveness of a single dose of mRNA vaccine estimated from realworld data is 70-80% in health care workers. Long term data regarding mRNA vaccine single dose efficacy is unknown, and based on current data, people should receive two doses of the mRNA vaccine to obtain the most benefit from vaccination. Vaccine breakthrough cases have occurred, including some cases of hospitalizations and deaths, but these are very rare. The CDC recently 18
SAN ANTONIO MEDICINE • July 2021
reported 0.001% breakthrough cases among 100 million people vaccinated and most of these cases did not result in hospitalization or death. Review is still ongoing to see who may be most at risk of breakthrough cases, but it is likely to be elderly or immunosuppressed persons. The safety record of the vaccines has also been good. Common side effects are typically within two days of the vaccine and include sore arm, headache, fatigue and less commonly, chills and fever. Reactogenic side effects such as chills and fever are more common after the second dose and in those < 55 years old. The Moderna vaccine can have a benign delayed local reaction at the site of injection 8-10 days after the vaccine, occurring in <1% of people. A side effect to be aware of for mRNA vaccines is anaphylaxis, which occurs in about 4 per 1 million persons vaccinated, and has been treated successfully at vaccine sites during the post-vaccine observation period. This occurs more commonly in women and those with a history of allergic reactions. If a severe reaction occurs within four hours of the first dose of the mRNA vaccine, the second dose should not be given. While the cause of these severe reactions is not known with certainty, polyethylene glycol (PEG) is a constituent of mRNA vaccines and is a known potential allergen. Those with a history of PEG allergy should avoid mRNA vaccines. The J&J vaccine does not contain PEG, but contains polysorbate which has potential cross-reactivity. For persons with a history of polysorbate allergy, consider an Allergy/Immunology consult or contact the CDC Clinical Immunization Safety Assessment Center for guidance. The detection of rare blood clots after the J&J vaccine demonstrates successful post-EUA surveillance with the Vaccine Adverse Event Reporting System (vaers.hhs.gov). The distinctive Thrombosis with Thrombocytopenia Syndrome (TTS) consists of a blood clot in an unusual location, such as the brain, in combination with thrombocytopenia, occurring within two weeks of the J&J vaccination. Women and those < 60 years old are at higher risk of this complication. An impor-
