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

18 SAN ANTONIO MEDICINE • July 2021