As the pandemic surged last year, getting a COVID-19 vaccine was a high priority. A year later, as more and more people got vaccinated and the FDA authorized booster doses, it might help to know which vaccine is more effective at keeping the disease at bay. Now, a recent study says that among the mRNA vaccines, Moderna's vaccine created twice as many antibodies as Pfizer's.
Before the COVID-19 pandemic, no messenger RNA (mRNA) vaccines were approved for use in humans. But the urgent need for vaccinations and the ability to make them at scale using the technology meant that mRNA vaccines got the necessary green light and were used to vaccinate most of the population in the U.S. As per the CDC data, out of approximately 370 million doses administered so far, approximately 354 million are mRNA vaccines, with the Pfizer vaccine used for over 209 million doses. While both companies claimed efficacies of above 90 percent for the vaccines from clinical trial data, there is no information available in the public domain that sheds light on their efficacy from real-world use scenarios.
Researchers at the Ziekenhuis Oost-Limburg, a non-university hospital in Gent, Belgium recruited hospital staff for a comparative study of the two vaccines. 1,647 individuals who had received both doses of an mRNA vaccine participated in the study that measured their antibody levels, prior to and 6-10 weeks after the second dose of vaccination was completed.
Of the participants, 688 were vaccinated with the Moderna vaccine while 959 were vaccinated with the Pfizer vaccine. Both groups included some individuals who had been infected with COVID-19, prior to vaccination and these individuals showed higher antibody levels, post-vaccination when compared to those who were not infected, prior to vaccination.
Among individuals who were not infected, those vaccinated with the Moderna vaccine showed higher antibody levels of up to 2881 units per milliliter (U/mL) as compared to the 1108 U/mL seen in Pfizer vaccinated individuals. According to a separate study published in Nature, antibody levels are predictive of the protection offered by the vaccines and therefore, the Moderna vaccine is likely to offer better protection against the disease. Whether the higher antibody levels also result in a longer duration of protection, needs to be further investigated, the researchers said in their paper.
There are two plausible reasons for the higher antibody levels of the Moderna vaccine, according to the paper. One is the higher amount of mRNA that is packed in the Moderna vaccine (100 micrograms) as compared to the 30 micrograms given in the Pfizer vaccine.
The other is the duration between the doses. While Pfizer vaccine is administered three weeks after the first dose, Moderna vaccine is administered after four weeks. A study conducted by Oxford University, which also has a COVID-19 vaccine approved and used in many countries but not in the U.S., shows that administering the second dose 45 weeks after the first one, resulted in an enhanced immune response.
Another finding from the study showed that among the uninfected antibody titers showed a negative correlation with age, meaning they were higher in younger individuals under the age of 35 and were reduced in older individuals.
In a separate pre-print publication that has not yet been peer-reviewed, researchers at Mayo Clinic suggest that the Moderna vaccine offered better protection in vaccinated individuals when compared to the Pfizer vaccine.