As growing numbers of people get vaccinated against Covid-19, growing numbers are also turning to social media with stories about side effects; we take a look at the facts.

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As growing numbers of us get vaccinated against Covid-19, social media is awash with conversations about side effects, which appear to be more common in young people. 

We take a look at what kind of side effects people can expect, the numbers, and what side effects might mean for immunity.

A Ministry of Health advisory says getting a Covid-19 vaccine is an important step we can all take to protect ourselves from the effects of the virus.

As with any vaccine, Pfizer may not fully protect everyone who gets it. Clinical trials performed on the Pfizer vaccine show it is approximately 95% effective against symptomatic Covid-19, seven days after receiving two doses.

Vaccines are just one part of our strategy to keep Covid-19 out of New Zealand, says the Ministry. We need to keep washing our hands, stay home if we're unwell and use the COVID Tracer App or keep a record of where we’ve been.

Why do side effects occur with vaccines?

Most coronavirus vaccines work by forcing the body to make the coronavirus spike protein, the part of the virus that allows it to bind to and invade cells. This then triggers an immune response. 

However, it takes a few days for the body to start producing the spike protein. This means that any immediate side effects experienced are probably a response to other vaccine components. 

Immune cells respond to these unfamiliar substances in the arm muscle by releasing signalling chemicals called cytokines to activate other parts of the immune system. The result is systemic inflammation, leading to aching, tiredness and in some cases a fever. 

“It’s a danger signal,” says Paul Morgan of the British Society for Immunology’s Covid-19 taskforce in an article published in New Scientist on Monday. 

“The body needs to be alerted that something is going on and primed to respond. It brings in the right sorts of cells to clear the damage or pathogen.”

Results collated from trials of all the approved vaccines point to younger adults being more likely to experience injection site and systemic reactions.  Morgan suggests this could be because older people have a weaker inflammatory response, as the immune system’s power wanes with age, he says. 

“Many countries initially prioritised vaccinating older people and moved to younger adults later, so this could be why social media is now awash with reports of systemic side effects.”

What about here in Aotearoa New Zealand?

Medsafe has been tracking ‘adverse events’, or side effects, following immunisation with Covid-19 vaccines. Up to 20 March this year, 35,031 Pfizer vaccines had been administered in New Zealand and 302 reports of side effects had been received. Some people reported multiple side effects, so the total number of people affected is lower.

The top 10 side effects reported were: dizziness (72), headache (58), nausea (53), fever (22), fainting (22), muscle pain (18), fatigue (17), arm pain (16), faintness (13) and chills (12).

Only ten of these reports were deemed serious. Nine of these were due to allergic reactions and were managed appropriately; one was a patient who experienced flu-like symptoms.

The Ministry of Health reported on 21 April side effects for the Pfizer vaccine had initially been identified during clinical trials, and then people were followed very closely for a period of two months after their second dose. Results were compared between people who had and hadn’t been vaccinated.

The Ministry also points to ongoing monitoring by an independent group of experts in order to understand long-term effectiveness, safety and side effects of the vaccine. Participants will have their health monitored for two years from the date of their second dose of the Pfizer vaccine.

Clinical trials and the Ministry’s own data show serious allergic reactions do happen, but are extremely rare, and the Ministry urges anyone who has had an allergic reaction to any vaccine or injection previously to talk to their vaccinator.

“(Allergic reactions) usually show soon after you’ve had your vaccine, which is why you need to wait at least 20 minutes. If you do have a serious allergic reaction, vaccinators are trained to manage these.”

The Ministry has information on its website about the different side effects and the best course of action should you experience any of them. The link is below.

What if I don’t get side effects? Does it mean my body hasn’t had an immune response?

Yes – and no, says Paul Morgan. 

In a study of people who received the Pfizer/BioNTech or Moderna vaccines, there were hints that those who had systemic effects after the second dose had higher levels of antibodies. But compared to those who had no effects, they didn’t show higher levels of a type of memory cell that triggers the production of antibodies, which helps maintain immunity to covid-19 in the months following vaccination. 

Morgan says people have great variability in their reactions to vaccines and those who notice no systemic effects have nothing to worry about. People will respond differently to inflammation, for instance, he says, but having no side effects doesn’t mean you haven’t built an immune response.

Our Ministry of Health urges anyone who is concerned to talk to a health professional. 

If you’re unsure about your symptoms or if they get worse, call your GP or Healthline on 0800 358 5453.

If you’re concerned about your safety, the Ministry advises you to call 111, and tell them you’ve had a COVID-19 vaccination so you can be assessed properly.

Click here to find out more about side effects, what to expect, and what to do if you get them.

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