The unprecedented vaccine rollout effort to help with the Covid pandemic has generated a stream of data about the possible side effects of each vaccine. What are the lesser-known side affects you need to know about?

Two days after getting the second Pfizer vaccine, Julie Mazenko felt a golf-ball size lump in her armpit.

She explained: “It was kind of painful and I touched and noticed that it was full of fluid.”

She then noticed a second swollen node in her neck and a third in the other arm.

Dr Laura Esserman is the director of UCSF's Breast Care Center and says Julie is not alone.

They're getting an influx of calls from women who are confusing swollen lymph nodes after the vaccine for signs of cancer.

"The lymph nodes when they get swollen, if you have an infection, are just doing their job. In the case of a vaccine, they are manufacturing the antibody for your body which is what you want," said Dr Esserman.

Most people get their vaccine in the shoulder area which is a part of the body with around 20 – 40 lymph nodes in that region.

Fatigue and headaches

The latest data from ZOE Covid Symptoms Study app looked at self-reported symptoms from 627,383 people after a jab between 8 December and 10 March.

The data found one in four people experience ‘mild, short lived’ side effects that mostly peaked within 24 hours and lasted one or two days.

The most common symptom was a headache, reported by eight percent and 13 percent after the first and second Pfizer dose, and 23 percent after the first AstraZeneca dose.

This was followed by fatigue, among eight percent and 14 percent of participants after the first and Pfizer dose, and 21 percent after the first AstraZeneca dose.