Why are my lymph nodes swollen? Plus every other question you have about boosters, answered.

Last month, Australian Technical Advisory Group on Immunisation (ATAGI) shifted its advice on COVID booster shots, reducing it from five months to four after the second vaccination, from January 4.

Since then, we’ve also had to deal with a wave of case numbers, the increasing threat of Omicron, and ever-changing restrictions. 

We’ve been confused. We've been anxious. We've been overwhelmed.

And now we have all the questions.

Watch: Epidemiologist Maria Van Kerkhove addresses the World Health Organisation. Post continues below. 

Video via @WHO/Twitter.

What are vaccine boosters? 

So, studies have shown that a reduction in our protection from COVID-19 occurs five months after our second primary vaccination. Therefore, an additional booster dose is recommended. 

In Australia, there are two booster doses that are readily available: Comirnaty (Pfizer) and Spikevax (Moderna). 

What you may be surprised to learn is that the booster is actually no different to the primary vaccinations; it’s all a matter of dosage. 

Leading infectious diseases expert Professor Sharon Lewin is director of Melbourne’s Doherty Institute in Melbourne, and co-chair of the National COVID-19 Health and Research Advisory Committee, which provides advice on Australia’s health response to the Commonwealth chief medical officer. (Yes, basically, she is very much in the know.)


As Professor Lewin told Mamamia, “The Pfizer third shot is exactly the same as dose one and two. The Moderna is a half dose.”

Professor Sharon Lewin. Image: Getty. 

Does everyone need a booster dose? How soon?

ATAGI recommends a booster dose for anyone who is 18 years and older, and has had their second COVID-19 vaccination dose at least four months ago.


For those with increased exposure risk (e.g occupational risk, those in outbreak areas or who have risk factors for severe disease), ATAGI stresses the booster dose is of particular importance. 

It also recommends the booster dose for people aged 18 years and over and who are severely immunocompromised, four months after their third dose.

And even if you’ve been infected with COVID-19 already, you still should get the booster, says Professor Lewin.

When do I get the booster if I've recently contracted COVID-19?

People who have been infected can be vaccinated as soon as they have recovered. 

Past infection reduces the risk of reinfection for at least six months. People who have prolonged symptoms from COVID-19 beyond 6 months after the initial illness can be vaccinated as well.

Pfizer or Moderna COVID-19 vaccines are the preferred vaccine for this booster dose, regardless of which vaccine was used for the primary course.

So, just how important is it to get the booster?

Professor Lewin puts it simply: 

“It is really important - especially with Omicron. Super important,” she reiterated.

Essentially, boosters provide us greater and earlier protection against infection from the virus that causes COVID-19, severe disease, and yes, even death. 

“The third shot gives you much higher levels of antibodies than the first two doses,” tells Professor Lewin. 

While it’s not mandatory, ATAGI believes the booster is vital in order “to mitigate against waning immunity” and the emergence of variants.


And according the Department of Health, a booster will not only provide protection, but it “should help prevent spread of the virus” too. 

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Israel was the first country to administer boosters in July. What lessons can we learn?

Professor Lewin says the key lessons have been “that boosters work in both reducing infection and reducing hospitalisations; and the risk of hospitalisation, especially in elderly populations.”

That’s right. As published in medical journal, The Lancet in October, “…Adding a third dose was estimated to be 93 per cent effective in preventing COVID-19-related admission to hospital, 92 per cent in preventing severe disease, and 81 per cent in preventing COVID-19-related death, as of seven or more days after the third dose.”

But how effective is the booster in protecting us against Omicron? And will it become mandatory?

Just as well, we have some data now starting to file in on that too. 

In December, director of the Infectious Diseases Unit at Israel’s Sheba Medical Centre, Gili Regev-Yochay, told Reuters“The good news is that with the booster dose it increases [protection] about a hundred fold. There is a significant protection of the booster dose, [but] it is lower than the neutralization ability against the Delta, about four times lower”. 

Numbers aside, Professor Lewin says another lesson Australia has observed from Israel, is that everyone who has had their first and second dose, “doesn’t automatically line up for their booster”.

As such, in October, Israel mandated the booster vaccine as a requirement for a valid digital vaccination passport.  


#Breaking: Initial data from Israel's Ministry of Health show that only 𝟎.𝟐% of the first 1.1 million recipients Pfizer/BioNTech 3rd jab were infected with the coronavirus. Only 88 such patients ended up seriously ill and less than 15 died. More evidence of need for booster.

Do we need the same brand of booster as we had for our first vaccinations? 

While Professor Lewin concedes there is a “theoretical benefit” to mixing, overall, she doesn’t believe it makes a difference.

Both Pfizer and Moderna are mRNA vaccinations, she points out, and “mRNA gives you the best boost, no matter what you had first” - even if that was AstraZeneca. 


Referring to a recent large UK study which tested nine different boosters on top of AZ/AZ or Pfizer/Pfizer, Professor Lewin continues, “All the vaccines that used mRNA, in either Pfizer or Moderna, gave the biggest boost of antibodies for both people that had AZ/AZ or had Pfizer/Pfizer.”

How safe are the booster doses? 

Early reports on the Pfizer booster show that the risk of heart inflammation - highest amongst young men - is reduced by “about half”, in comparison to the second dose, tells Professor Lewin. 

Laura was eager to get her booster in December before visiting her family in the UK over Christmas.

“I didn't really have any side effects apart from a sore arm and maybe a bit of fatigue, so I was lucky!,” she told Mamamia.

“I feel very reassured - especially now in the face of the Omicron variant, and know I have done as much as I can to protect myself, my family and the wider community."

Image: Getty. 


Will the booster be our final vaccination against COVID? Or will it become like the annual flu shot?

Basically, it’s still too soon to tell. 

ATAGI says, “There remains uncertainty about the duration of protection following a booster dose, and the potential emergence of future new variants”.

Professor Lewin adds, “Whether this is a three dose regimen to give you a really good, durable immunity, or whether there'll be annual boosters, we just don't know.”

How long until we do know?

Probably over the next few months as more data filters through, she anticipates.

Why do I have a swollen lymph nodes after my COVID-19 booster?

If you've noticed your lymph nodes swell up after your booster shot, you're not alone. 

According to the Therapeutic Goods Administration's first COVID-19 vaccine safety report of 2022, swollen lymph nodes (also called lymphadenopathy) were "the most common adverse event reported" after a booster shot. 

The good news? This is a "normal and known side effect of vaccines and occurs when the immune system is stimulated". 


As Sydney GP, Dr Brad McKay, explains, "The purpose of any vaccine is to cause an immune reaction. Each immunisation teaches your white cells to identify what an intruder looks like and trains them to fight off future attacks."

"This reaction generally goes under the radar, occurring quietly beneath the surface of your skin, but some people actually get to see this 'white cell training camp' occurring in real life," he told Mamamia

"The mRNA COVID-19 vaccines (i.e. Pfizer or Moderna) sometimes cause an overactive inflammatory response. This causes the lymph nodes in the armpit to swell up and become tender. This immune reaction tends to be more uncomfortable than painful and occurs mainly on the side of the body where the vaccine was injected."

But it doesn't last very long. 

"The swelling and tenderness is only transient and usually settles within a few days," he said. 

How do I go about getting a booster?

You may have already received a letter encouraging vaccine boosters from the federal government, or perhaps a text message reminder from your state government. In any case, if you're eligible, get cracking, and book a booster dose. How? Call your GP or use the COVID-19 Clinic Finder.

This article was originally published on December 17, 2021, and was updated on January, 20, 2022.

Feature Image: Getty.

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