In America, the holidays have arrived with two authorized COVID-19 vaccines. Both come in small, shiny vials, and offer much hope in a grisly year. Now comes the hard part: One is from Aunt Pfizer, the other from Uncle Moderna. Which one should you take?
Gratefully, overall the two vaccines are functionally siblings — they even share a genetic strategy of building natural immunity to the virus based on modRNA vaccine technology. They are both two-dose vaccines composed of basic ingredients including fats, salts, sugar and modRNA. Both have undergone animal studies, and are in phase 3 of clinical trials, having already been tested in tens of thousands of people of all genders, race and ethnicities. Additionally, both vaccines demonstrate up to roughly 95% in early efficacy. Thus far, whatever their differences, the debate seems to be whether they went to Harvard or Yale, not that one attended Trump University.
There are, however, a few distinctions worth noting. For Moderna, the vaccine holds an early edge for a possible stronger reduction in severity of symptoms, as well as a higher single dose efficacy in early trials (80.2% to Pfizer’s 52.4%). On the other hand, Pfizer is authorized for a wider age range (age 16 to Moderna’s 18) and may have a slightly higher efficacy for people ages 65 and up, although both are robust, at Pfizer’s 95% and Moderna’s 86.4%. These slight differences are still being evaluated for statistical significance, and could grow or narrow over time. Any differences that remain will likely be attributable to minor chemical variations, such as the specific lipid nanoparticles (fats) or modifications of the nucleosides for the mRNA. These same small differences are why Moderna’s vaccine does not require the extra cold storage that Pfizer’s does, a feat the company attributes to having developed a specialty in modRNA therapeutics (note the company’s name) via production of 10 prior modRNA vaccine candidates.
Regarding safety concerns, early clinical trials suggest both vaccines are overwhelmingly safe for general populations, with possible symptoms typically reflecting a common immune response such as headache, fatigue, fever and muscle soreness. Upon wider distribution of the Pfizer vaccine, only six known cases in over 272,000 administrations to date in the United States have resulted in temporary severe allergic reactions. While this is slightly higher than is often seen for other vaccines, which come in at roughly one in a million, it still represents a very small fraction of people. In comparison, COVID-19 has already infected over 18.2 million Americans — many of whom experience lasting debilitating symptoms — and has outright killed over 320,000 in less than a year.
Still, to address this safety concern, patients with a history of severe allergies — most notably to any of the ingredients in the vaccine — or who are immunocompromised, are recommended to discuss with their health care providers and determine individual risks. Additionally, upon receiving the vaccine, recipients are recommended to wait 30 minutes in the health care setting upon administration to ensure safe delivery.
Other potential demographic limitations include women who are pregnant or lactating. Clinical trials have not yet been completed for either, although Moderna has completed animal studies without concerns of fetal impact. Pfizer has interim data from animal studies which also show no concerns to date. Given the potential risks of COVID-19, the FDA currently recommends women also discuss with their health care providers. Of note, people designated as higher-risk categories may especially want to consider participating in a clinical trial to help establish data.
At the end of the day, the Pfizer and Moderna vaccines are a family affair, having both demonstrated far more good than harm. With overall access limited for months to come, front-line workers and other early adopters are likely to have the choice made for them based on practicalities such as the slight difference in distribution and storage requirements. For example, in addition to requiring extra cold freezers, Pfizer’s vaccine also requires purchase in bulk at 975 doses. In contrast, Moderna’s vaccine requires standard freezers and only 100 doses per purchase order. This might make the Pfizer vaccine more readily available in larger, more dense populations, while the Moderna vaccine may be more easily accessible for smaller facilities or rural areas. For more information on local vaccine distribution contact your local health department.
Regardless of which favorite aunt or uncle you get it from, it’s finally almost time to roll up your sleeve and proudly show off those flabby quarantine biceps — they are, after all, a sign of your commitment to staying home and saving lives.