COVID-19 vaccination side effects: how to manage and when to report them

Three COVID-19 vaccines have been provisionally approved and are currently being used in Australia’s COVID-19 vaccination rollout: the mRNA vaccines Comirnaty by Pfizer/BioNTech and Spikevax (elasomeran) by Moderna Australia PTY Ltd; and Vaxzevria by AstraZeneca.^1,2,3 COVID-19 vaccines delivered as part of the rollout are free for everyone living in Australia and no consultation fee is charged.

The AstraZeneca vaccine is recommended for people aged 60 years and over*,⁴ or aged 18 to 59 in outbreak areas if they do not have immediate access to Comirnaty (Pfizer) or Spikevax (Moderna). The mRNA vaccines from Pfizer and Moderna are recommended for people 12 years and over. Both types of vaccine are given in two doses, with 3–6 weeks between doses of the Pfizer vaccine, 4 weeks between doses of the Moderna vaccine, and at least 12 weeks* between doses of the AstraZeneca vaccine.⁵ The age and dose interval recommendations have been made by ATAGI according to current national and overseas evidence. Please note that the age and dose intervals described in the provisional approval documents for these vaccines may be different to the ATAGI recommendations.

A fourth vaccine – COVID-19 Vaccine Janssen (available as Johnson & Johnson COVID-19 vaccine overseas) – has also received provisional approval for use in Australia, but is not part of the national rollout.^6,7 No recommendations about the use of the vaccine have been released.

* These recommendations remain unchanged for areas in Australia not currently experiencing a COVID-19 outbreak (increased community cases). However, for areas where a COVID-19 outbreak is happening, the recommendations are different because the chances of infection are greater. The key changes in recommendations are that:⁸

• adults under 60 years of age who have not been vaccinated should speak with a GP to consider if the benefits of an AstraZeneca vaccine are greater than any potential risk of unwanted side effects – this is especially important if the Pfizer vaccine is hard to access, and
• the time between receiving the first and second doses of the AstraZeneca vaccine can be reduced to between 4 and 8 weeks. This can help to increase the number of people who become fully vaccinated over a shorter period of time.

Vaccines mimic infection and stimulate a person’s immune system to produce antibodies against a virus or bacteria, without the person experiencing the actual infection.⁹ Once a person has the antibodies, their immune system is better able to protect them if they are exposed to that particular virus or bacteria in the future.

On average, it can take up to 14 days after a vaccination for best possible protection to develop.⁹ This is why people are encouraged to continue practicing COVID-19-safe hygiene (hand washing, physical distancing, mask wearing, etc) after they receive their COVID-19 vaccine.

To make antibodies, the immune system goes through a number of complex steps, including making proteins called chemokines and cytokines that can influence how cells in the body behave.¹⁰ These steps are important to the production of antibodies, but they can also lead to common side effects such as raised body temperature (fever), headache, muscle soreness and shivering (chills).

While we may find these signs and symptoms unwelcome and uncomfortable, they are typical responses that show our immune systems are responding to a potential ‘threat’ and working hard to protect us from further illness. In fact, recent research suggests that some increase in body temperature (such as mild fever) may actually help switch part of the immune system on and assist in the body’s response to vaccination.^11,12

Because of this desired immune response, flu-like symptoms can be a side effect of any vaccine and COVID-19 vaccines are no different.

Inflammation is also part of the immune response and can result in local side effects such as swelling, redness or pain at the injection site.¹⁰ These signs and symptoms are often called injection site reactions if they occur after a medicine (eg insulin) or a vaccine has been given. They are the same signs and symptoms you would experience after a mosquito bite for example.

“So, mild fever, muscle aches, tiredness or inflammation are common ways for your body to indicate it is having an immune response to something in your environment,” says Dr Anna Samecki, medical adviser at NPS MedicineWise.

“They are also common signs and symptoms that people may experience following vaccination.

“Essentially, the immune system can’t tell the difference between a virus that you have picked up through person-to-person contact, or an inactivated version or piece of that virus that is present in a vaccine. It responds in a similar way to both,” she says.

Watch a video from the World Health Organization about why some people have side effects after vaccination

It is also important to realise that not everyone experiences a disease in the same way. 

Using COVID-19 infection as an example, we have seen some people hardly affected at all, some people experiencing mild symptoms, and others experiencing severe symptoms requiring hospital admission. There are many reasons why people respond differently to the same disease – age, general health, gender and previous immunity may all contribute.⁷ 

In the same way, there will be a range of responses to a particular vaccine, with some people having few or no signs or symptoms, and others experiencing some or many.

With the current focus on COVID-19 vaccines, Healthdirect Australia has developed the COVID-19 vaccine symptom checker to help you decide what to do if you have side effects after a COVID-19 vaccination, ranging from common flu-like symptoms to rare cases when medical attention is needed.

Mild side effects

Evidence from clinical trials, along with national and international databases, show that most side effects being reported after vaccination with AstraZeneca, Moderna and Pfizer COVID-19 vaccines are mild and temporary (lasting only a few days).^13-16

National survey data from more than 4,568,620 Australians (information correct to 7 November 2021) who have received either one or both doses of a COVID-19 vaccine shows that for the AstraZeneca vaccine, around 6 in 10 people (56%) reported experiencing side effects after the first dose and around 3 in 10 (25%) after the second dose.¹⁷ For the Pfizer vaccine, this trend was reversed, with 4 in 10 people (36%) experiencing symptoms after the first dose and 5 in 10 (54%) after the second dose.¹⁷ For the Moderna vaccine, around 4 in 10 (40%) people reported experiencing side effects after their first dose and around 6 in 10 people (65%) after the second dose.¹⁷

Potential side effects include those described above such as fever, headaches, muscle and joint pain as well as injection site reactions (pain, redness, swelling or hardness where the needle went in). Other possible side effects being described for all three vaccines also include nausea and tiredness (fatigue).¹⁷

“Usually rest is the best advice for managing mild vaccine-related side effects,” says Dr Samecki.

“If you have a fever, you should stay well hydrated, keep the room at a comfortable temperature, wear lightweight clothing and avoid using warm bedding as it may make you hotter.

“There is no need to take medicines for pain or fever unless you are uncomfortable. However, if you are feeling discomfort, simple pain relievers such as paracetamol and ibuprofen are available over the counter without a prescription and can help reduce pain and fever.

“Before taking any medicine, check the active ingredients are safe to take with any medical conditions you have, other medicines you are taking, or if you are pregnant or breastfeeding,” she says.

When to seek medical attention

New, unexpected or persistent symptoms

Speak with a health professional if you are worried about a potential vaccine side effect, have new or unexpected symptoms, or if you have an expected side effect that hasn’t gone away after a few days. 

The COVID-19 vaccine side effects symptom checker can help and you can contact the Adverse Medicine Events line for information about side effects and to forward reports to the TGA. The service is, however, unable to provide medical advice.

Symptoms more than 4 days after vaccination

A very rare condition called thrombosis with thrombocytopenia syndrome (TTS) has been reported as confirmed or probable in 139 Australians who receive their first dose of the AstraZeneca COVID-19 vaccine (information correct to 7 November 2021).¹⁸ There have been over 13.2 million doses of the AstraZeneca vaccine given. Australian data show that the risk of this very rare side effect is lower in people that are older. It appears that the condition is also more severe in younger people.¹⁹ Current estimates (on 7 November 2021) of risk are summarised in the following table. 

The key signs of this adverse event are blood clotting (thrombosis) and low platelet levels (thrombocytopenia).¹⁸ First reports of this rare condition emerged from Europe in April 2021²⁰ and medicine regulators both here and overseas continue to monitor the issue and investigate reports of potential events.¹⁹ A consequence of this monitoring is that information about the condition continues to grow and there are now established procedures to help treat people who develop this condition. Health professionals are now fully alert to the potential of TTS and are more likely to diagnose it earlier. Raised awareness, early diagnosis and appropriate treatment have meant that most people who experience this extremely rare condition return to good health.^18,19

Symptoms for TTS typically occur around 4 to 28 days after vaccination.⁵ You need to seek medical attention, and if severe, go to a hospital emergency department, if you have any of the following symptoms, particularly 4 to 28 days after vaccination:

• severe, persistent headaches that do not settle with paracetamol or other pain reliever medicines
• blurred vision
• difficulty with speech
• confusion or seizure
• shortness of breath
• chest pain
• persistent abdominal pain
• leg swelling
• rash or bruising not at the injection site that cannot be explained.²¹

Myocarditis/pericarditis

 Myocarditis (inflammation of the heart) and pericarditis (inflammation of the membrane around the heart) are rare side effects that typically occur within 10 days of vaccination with the Pfizer or Moderna mRNA vaccines. Cases are usually short lived and resolve following treatment and rest.

To 7 November 2021, 511 reports of suspected myocarditis alone or in combination with pericarditis – and 1202 reports of suspected pericarditis alone –have been recorded in Australians who received the Pfizer vaccine. For Moderna, 19 reports of suspected myocarditis and 46 reports of suspected pericarditis have been recorded.¹⁸ Reporting of myocarditis appears to be more common in teenage boys after the second dose of the Pfizer vaccine (seven cases in 100,000 people) compared with the general population after a first or second dose (one in 100,000 people).¹⁸

Myocarditis and pericarditis symptoms include chest pain, palpitations (irregular heartbeat), fainting or shortness of breath, and usually occur within 1–5 days of vaccination. 

Seek medical attention if you experience any of these symptoms

Severe allergic reactions

Serious but extremely rare side effects to vaccines – including the COVID-19 vaccines – can include allergic reactions. If an allergic reaction is going to happen it will usually occur within 15 minutes of receiving a vaccine, which is why you should wait this amount of time before you leave the vaccination centre.

Seek medical attention if you think you are having an allergic reaction and call 000 if the symptoms are severe, such as if you have difficulty breathing, start wheezing, have a fast heartbeat or feel like you may be about to collapse.

All vaccines available for prescription in Australia have to undergo approval and regulatory processes. These processes are conducted by the TGA to make sure the vaccine is safe for human use and of the highest quality.²²

The reporting of side effects, also known as adverse events, is an important way the TGA can identify previously unknown safety issues, including situations when a vaccine should not be used and interactions with medicines or other vaccines.²²

How to report an adverse event

You can report adverse events to your healthcare provider and ask them to report on your behalf, or you can report to the NPS MedicineWise Adverse Medicine Events Line on 1300 134 237 (8 am–8 pm AEST/AEDT 7 days a week). Alternatively, you can report to your State or Territory health department or directly to the TGA.

Visit the TGA’s COVID-19 vaccine page for more information.

Why do we need to report adverse events?

Any vaccine, including the COVID-19 vaccines, is only approved when it meets high quality standards and has been shown in clinical studies of sufficient size and rigour to be safe and effective. NPS MedicineWise has more information about clinical trials, why they are important and their role in the approval of medicines and vaccines for use in Australia.

Clinical trials are a very important part of understanding the effects and the safety of a medicine or a vaccine, but they cannot detect all possible harms:

They will not be able to detect adverse events that take longer to develop than the length of the trial.

A very rare adverse event may not be detected if it is so rare that it didn’t happen to anyone in the trial.

Also, some population groups (like children, older people, pregnant women, people with specific health conditions) may have been excluded from taking part in the clinical trial, and so any adverse effects that only occur in these groups would not be known from the clinical trials.

What to report and what happens to the information

Adverse event reporting is an important way the TGA continuously monitors and evaluates the safety and effectiveness of vaccines to add to what we know from clinical trials.

The link between the AstraZeneca COVID-19 vaccine and extremely rare cases of TTS was identified as a result of the high-quality adverse event reporting systems in Australia and overseas. Since this discovery, effective treatments have been found and, together with the raised awareness and early diagnosis, most people who experience TTS recover to good health. This is an example of how adverse event reporting systems work to help protect the public.

If you or your doctor think a COVID-19 vaccine has caused a side effect, especially if it is unexpected or significant, you are encouraged to report it.

The TGA is particularly interested in reports of the vaccine interacting with a medicine, any adverse effects that are not already known, any serious health outcomes or any adverse reactions that lead to further investigation.

Each adverse event report is entered into the Australian Adverse Drug Reaction System (ADRS) database.

If a particular adverse event is reported a number of times, it may be flagged for further investigation and prioritised according to risk. If identified as a safety risk, the TGA decides what action to take. Depending on the impact on public health, the TGA may issue safety alerts to health professionals and the public. It may also remove the vaccine from use or restrict the people who can use it.²¹

As well as adverse event reporting, the TGA monitors the latest clinical studies and scientific reports, undertakes testing, and works with regulators from other countries (like the US Food and Drug Administration) to identify any new potential safety issues.

A broad rollout of COVID-19 vaccines in Australia has a key role to play in protecting Australian’s health during the pandemic. New COVID-19 variants appearing and hopes of more global travel mean the situation is constantly evolving.

The reporting of potential adverse events after vaccination is part of the way we make sure we get the most benefit out of vaccines safely. Pharmaceutical companies, public and private health service organisations, health professionals, carers and consumers all have a role to play. The transparent way this is done is important to maintain trust in the vaccines. Trust, in turn, is important to ensure as many people as possible choose to be vaccinated, providing the best possible protection against COVID-19 for the Australian population.

Shared responsibility in action

Since the Australian COVID-19 vaccine rollout began in February 2021, key experts working with groups such as the TGA and ATAGI have been constantly monitoring reported side effects – both mild and more serious. This information, combined with data emerging from international experience, has been used to make sure recommendations about the use of available COVID-19 vaccines balances any potential risk from vaccination against the need to protect individuals and the community against the ongoing threat of COVID-19.

To date this monitoring has led to two key changes in recommendations. Firstly in April 2021 when the AstraZeneca COVID-19 vaccine became the preferred vaccine for people aged 50 years and above, and most recently 17 June 2021, when that age range was further revised to people aged 60 years and above.

You can read the latest statement from ATAGI.

Information about COVID-19 vaccines

• Use the Eligibility Checker by the Department of Health
• Read the resources on COVID-19 vaccines by the Department of Health, including ‘What happens after I am vaccinated for COVID-19?’
• Find out more about COVID-19 vaccines on our website
• Read frequently asked questions about COVID-19 vaccines by the National Centre for Immunisation Research and Surveillance

Information about vaccines and adverse events

• To report or ask questions about any medicine or vaccine related side effect, call NPS MedicineWise Adverse Medicine Events (AME) Line on 1300 134 237, 7 days a week 8 am – 8 pm AEST/AEDT
• Report an adverse reaction to a vaccine by filling out an online form on the TGA’s website