COVID-19 vaccine safety: Biggest microscope yet finds little new

COVID-19

John D. Grabenstein, RPh, PhD, FAPhA

Results of a COVID-19 vaccine safety study that included over 99 million patients from eight countries were released in February 2024.

News headlines were generally accurate, but the sample below shows how some titles were misleading:

• “Largest COVID vaccine study ever reveals the actual health risks you face”
• “Covid-19: Two rare vaccine side effects detected in large global study”
• “Largest multicountry COVID study links vaccines to potential adverse effects”
• “Study of 99 million COVID-vaccinated people finds links to brain, heart problems”
• “Despite sensational reports, COVID-19 vaccine safety outweighs risks”
• “Covid vaccines linked to small increase in heart and brain disorders, study finds—but risk from infection is far higher”

What most of these headlines lack is perspective. Most of the links to adverse effects reported in these news items were for vaccines distributed outside the United States, and the new connections discovered and relevant to the United States are not confirmed cause-and-effect relationships.

All medications carry risks. But how can we ignore the benefits? COVID-19 vaccinations prevented more than 18 million hospitalizations and 3 million deaths in the United States alone, and even more globally.

So, as pharmacists engage with their patients, it is helpful to keep in mind these details about the 99-million-vaccinee study specifically and the U.S. vaccine safety surveillance program in general.

COVID-19 vaccines and the Global Vaccine Data Network study

To complete the study, the Global Vaccine Data Network (GVDN) compiled data from 10 sites across eight countries (not including the United States), comparing observed and expected rates of 13 adverse events among 99,068,901 COVID-19 vaccine recipients.

This study confirmed the rare association between mRNA COVID-19 vaccines and myocarditis that U.S. officials have been educating clinicians and the public about since 2021. GVDN researchers also showed there is no link between mRNA vaccination and Guillain-Barré syndrome, transverse myelitis, Bell’s palsy, convulsions, febrile seizures, various forms of thrombosis, or pulmonary embolism.

A signal for risk of acute disseminated encephalomyelitis that requires further study was identified. Seven cases were found after 10 million first doses of
Moderna’s mRNA vaccine in these databases, whereas two cases were expected. Other studies—including a companion study —did not find such an association, so this remains a signal rather than a confirmed risk.

The remarkably large number of vaccinees in the GVDN paper allowed the researchers to apply one of the biggest “microscopes” yet to assess very rare events. The other safety signals identified are so very rare that even if they turn out to have a cause-and-effect relationship, they would need to be compared to the risks of driving across town to be vaccinated.

The U.S. Vaccine Safety Surveillance Program

CDC coordinates an overlapping set of vaccine safety surveillance programs, partnering with other government agencies and multiple universities and health systems. The surveillance program encompasses more than a dozen projects and fulfills an important public responsibility: to keep eyes and ears open for unexpected findings. Where any one program has a limitation, another program among the set has a corresponding strength to bear.

CDC and its partners have presented their safety findings at each public meeting of ACIP since late 2020—at least 30 meetings. That scrutiny assesses more than 700 million COVID-19 vaccinations administered in the United States since December 2020.  

The common adverse events, those happening at rates of 1 per 100 up to 1 per 10,000 vaccinations, attributable to COVID-19 vaccination are very well understood. Even so, the nation’s eyes and ears remain open to learn about even rarer events or events that happen in subsets of the population. All in all, vaccines are medications that carry risks and benefits. COVID-19 vaccination remains the best, most reliable way to prevent a serious COVID-19 infection, hospitalization, or death.

Perspective

Four years after the pandemic started, several thousand Americans continue to be hospitalized each week due to COVID-19 infection. Many of those hospitalizations could be prevented by wider use of COVID-19 vaccines.

The risks from vaccination pale in comparison to the risk from COVID-19. Pharmacists and their teammates are the leading COVID-19 vaccination providers in America.

Remember to read the full details, rather than assuming the headline tells the whole story. ■

References 

1. Faksova K, Walsh D, Jiang Y, et al. COVID-19 vaccines and adverse events of special interest: A multinational Global Vaccine Data Network (GVDN) cohort study of 99 million vaccinated individuals. Vaccine. 2024 :S0264-410X(24)00127-0.

2. Dyer R. Largest COVID vaccine study ever reveals the actual health risks you face. N.d.: Science Alerts. Available at: www.sciencealert.com/largest-covid-vaccine-study-ever-reveals-the-actual-health-risks-you-face. Accessed March 10, 2024.
3. Wise J. Covid-19: Two rare vaccine side effects detected in large global study. BMJ. 2024 Feb 26;384:q488.
4. Choi J. Largest multicountry COVID study links vaccines to potential adverse effects. N.d.: The Hill. Available at: https://thehill.com/policy/healthcare/4477406-largest-multi-country-covid-study-links-vaccines-to-potential-adverse-effects/. Accessed March 10, 2024.
5. Staff. Study of 99 million COVID-vaccinated people finds links to brain, heart problems. N.d.: Washington Times. Available at: www.washingtontimes.com/news/2024/feb/19/study-99-million-covid-vaccinated-people-finds-lin/. Accessed March 10, 2024.
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7. Johnson A. Covid vaccines linked to small increase in heart and brain disorders, study finds—But risk from infection is far higher. Jersey City, NJ: Forbes. Available at: www.forbes.com/sites/ariannajohnson/2024/02/19/covid-vaccines-linked-to-small-increase-in-heart-and-brain-disorders-study-finds-but-risk-from-infection-is-far-higher/?sh=59a4cd0860ff. Accessed March 10, 2024.
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9. WHO European Respiratory Surveillance Network. Estimated number of lives directly saved by COVID-19 vaccination programs in the WHO European Region, December 2020 to March 2023. medRxiv. 2024; [Epub ahead of print]. doi: https://doi.org/10.1101/2024.01.12.24301206/
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