Why the Pfizer vaccine has fewer side effects

Top scientists at the pharmaceutical company Pfizer have used the active ingredient dosage inVaccineCovid-19 dose is lower than in Moderna vaccine.

Pfizer's Covid-19 vaccine has 30mcg of mRNA, while Moderna's has 100mcg. Experts have speculated that this may be one reason why Pfizer's vaccine has produced a lower antibody response than Moderna's in recent studies.

Philip Dormitzer - Pfizer's chief scientific officer explained that Pfizer and BioNTech used the minimum dose but still got a stronger immune response when infected with Covid-19.

Higher doses may cause more side effects, Dormitzer added.

According to the US Centers for Disease Control and Prevention (CDC), the Pfizer and Moderna Covid-19 vaccines cause similar side effects. The two mRNA vaccines can cause people who receive the vaccine to experience arm pain, rash, muscle pain, fatigue, and mild fever.

Illustration: Iamexpat

According to the CDC, an extremely rare side effect of the mRNA vaccine is myocarditis, which is quickly resolved.

Doctors also noted the phenomenon of “Moderna arm,” a red rash that appears after vaccination but will disappear on its own.

The US has administered more than 214 million doses of Pfizer and 147 million doses of Moderna.

Moderna vaccine boosts antibodies higher than Pfizer

According to a study of 1,600 Belgian health workers published in the Journal of the American Medical Association on August 30, the Moderna vaccine produced twice the amount of antibodies as Pfizer's 6 to 10 weeks after vaccination.

The authors said the higher mRNA concentration in the Moderna vaccine and longer interval between doses may explain this difference.

A study from the University of Virginia published in JAMA on September 2 found no difference in antibody responses among age groups to the Moderna vaccine. Meanwhile, antibody responses were lower in people 50 and older with Pfizer. The researchers said the difference may be related to the amount of mRNA in the vaccine.

Covid-19 vaccination for epidemic prevention and control forces in Vinh city. Photo courtesy of Thanh Chung

The antibody response is only one aspect of the immune system and the level of antibodies needed to protect against Covid-19 is not yet known.

Vaccine protection also depends on whether the antibody response changes over time. A recent study from the University of Oxford found that the Pfizer and AstraZeneca vaccines produced consistent levels of antibodies over four months. After that, the levels of antibodies from the Pfizer vaccine declined, while those from the AstraZeneca vaccine remained the same.

According to real-world data from Canada earlier this year, after one dose, Pfizer's vaccine was 56% effective against symptomatic Covid-19 caused by the Delta variant, while Moderna's was 72%.

Other factors could have influenced the results, including the fact that the Pfizer vaccine is typically given to older adults, who tend to mount a weaker immune response.