WHEN healthcare student Melanie Hui, 21, got her first dose of the Pfizer vaccine in February, her arm was so sore she could not lift it to tie her hair.
Hui, who is also a cross country runner, said she also felt fatigued and had headaches for about two days after the jab.
But when her grandmother, retiree Margaret Choong, 72, received her first dose of the Moderna vaccine last month, all she felt was a little pain at the injection site on her arm.
Their experiences reflect the results of clinical trials for both the Pfizer and Moderna vaccines which showed that younger adults like Hui tend to report more frequent and severe side effects than older people after their jabs.
In Pfizer’s trials, those aged 18 to 55 reported experiencing side effects such as fever, fatigue, headaches and pain at the injection site more frequently than those aged 56 and above.
A similar trend was observed for the Moderna vaccine.
Assoc Prof Hsu Li Yang, vice-dean of global health at the NUS Saw Swee Hock School of Public Health, said side effects tend to be more pronounced in those with more robust immune systems, such as young people and women.
He added: “Common side effects such as arm pain, muscle ache, fever, headaches and fatigue are the results of reactogenicity – the physical manifestation of our immune systems reacting to vaccination.”
This does not mean the vaccine is less effective in those who do not experience side effects.
Prof Hsu said: “There is no correlation between absence or presence of these reactogenic side effects and vaccine efficacy. So, those with no side effects are just as likely to be protected by the vaccine.” — The Straits Times/ANN