How long do effects last after vaccine?

Like with any vaccination, there is potential for side effects after you get your shot. The good news is that the COVID-19 vaccines have similar side effects that are typically mild and don’t last long — about one to three days.

The most common side effects include a sore arm, fatigue (feeling tired), headache, aches, and fever. Severe side effects are very rare and treatable.

It is difficult to predict. Side effects are more common, and may be more pronounced, after the second dose of Pfizer-BioNTech COVID-19 vaccine (Comirnaty®) or Moderna COVID-19 vaccine (Spikevax™).

If you get side effects, they are a good sign — they indicate that the vaccine is working by triggering the immune system.

When you get vaccinated, your immune system recognizes something as being foreign. The immune system automatically launches a small-scale attack against it. This process teaches your immune cells to recognize and respond to an “invader.” That’s why you might experience some side effects. Think of it this way: The body’s response to the vaccine is like a training mission for the real fight.

Once you’re fully vaccinated, if you were infected by the virus causing COVID-19, your immune system would be ready to launch an even larger and more powerful attack to protect you.

If you don’t experience any side effects, that doesn’t mean that the vaccine didn’t work. In the vaccine clinical trials, more than half of people didn’t experience any side effects but we still know that the vaccine was effective in those people.

If you have pain or discomfort after receiving your vaccination, talk to your doctor about taking an over-the-counter medicine, such as ibuprofen (Advil) or acetaminophen (Tylenol).

To reduce pain and discomfort on your arm:

In most cases, discomfort from fever or pain is normal. Contact your doctor or healthcare provider:

You should wait until after being vaccinated to see how you feel. If you do experience side effects, it is OK to take an over-the-counter drug (like Advil or Tylenol) to lower a fever, reduce chills, or relieve a headache or body aches. It’s important that you do not take these drugs before getting your vaccine as there are theoretical concerns that some pain relieving drugs may interfere with the immune response to the vaccine. It is also unclear if taking medication ahead of time actually works to reduce post-vaccine symptoms.

A few extremely rare instances of severe side effects have emerged and been investigated, but scientists have concluded the risk of getting severely ill from COVID-19 is far greater than the risk of these side effects. Here is proof of this careful and ongoing scrutiny:

Some people may experience some swelling or tenderness in their lymph nodes. It is also possible that this swelling will show up on imaging tests and could be mistaken for progression of  certain cancers — primarily breast, head and neck, melanoma, and lymphoma.

This vaccine side effect is more common after the second dose, usually occurs within 2 to 4 days after the vaccination, and can last for an average of 10 days.

On imaging tests, the lymph node enlargement may be detected for a longer period. For these reasons, we recommend:

It’s important to know that all kinds of vaccines can cause temporary swelling of the lymph nodes, which may be a sign that the body is making antibodies in response as intended.

Should I get an antibody test after the vaccine to make sure it’s working?

Antibody testing is not currently recommended check someone’s immunity to COVID-19 following vaccination. The COVID-19 antibody test used at MSK detects the immune response after being infected by COVID-19. It does not measure immunity that results from the vaccine. That’s why it should not be routinely ordered to assess vaccine response.

The COVID-19 vaccines are among the most effective vaccines in history. They are as effective — if not more — than vaccines for polio, chicken pox, measles and the flu.

The chances of getting sick after vaccination are minimal. Studies show even if you develop COVID-19 after being vaccinated, you are unlikely to get severely ill. Flu vaccines are less effective than the COVID vaccines, but they can protect you from more severe flu illness and hospitalization. The COVID-19 vaccines are even more powerful.

Learn more about the COVID-19 vaccines » 

August 8, 2022

Additional Resources

• Anaphylaxis – an immediate allergic reaction. This is dramatic but rare (fewer than one in a million people will have anaphylaxis after a vaccination), and it is completely reversible if treated quickly.
• Febrile seizure – this seizure usually lasts one or 2 minutes. It can be frightening and usually does not cause permanent harm or have lasting effects. It is caused when a child’s fever rises quickly.
• Bowel blockage (intussusception) – this occurs in the 7 days following the first and second dose of rotavirus vaccine. This is a rare side effect for about 1 in 17,000 babies.

If any other reactions are severe and persistent, or if you are worried, contact your GP (doctor) immediately or dial triple zero (000).

Safety testing and re-testing of immunisations

Millions of people – many of them babies and young children – are immunised every year, with no side effects.

Other people may experience mild common side effects.

You can be sure the immunisations used in Australia are safe. There are rigorous safety research and testing processes that all new vaccines must pass before they’re registered. Every vaccine is manufactured and tested according to strict safety guidelines.

And, we keep monitoring vaccines, even after they’re registered and being used. The Therapeutic Goods Administration (TGA) conducts detailed surveillance to make sure vaccines stay safe and effective.

If the TGA has any concerns about a vaccine, it revokes the vaccine’s registration and withdraws it from the market.

Think of it this way – a vaccine is a medicine that we use to stop ourselves and those in our care from getting sick. We are much less likely to get an illness if we are immunised.

Immunisations are medicine. Like any medicine, they can cause mild side effects. In rare cases, they can cause more serious side effects, but the chance of an immunisation seriously harming us is rare.

Deciding not to be immunised puts you, loved ones and the community at risk of unnecessarily catching an infectious disease that can be very serious and even deadly.

There’s a lot of information available about immunisation, and it’s easy for us to feel overwhelmed or not know where to start.

If you have questions, a good first step is to talk to your GP (doctor). If you have young children, maternal and child health nurses, or paediatricians can also help. They can explain how vaccines work, discuss the benefits of immunisation and the risks of disease, and outline your options.

Before you agree to any vaccines, your immunisation provider has to give you all the information you need to make an informed decision. Your consent must be voluntary, without any pressure, coercion or manipulation. And you do not have to give your consent until your immunisation provider has explained the risks and benefits.

Remember, you can take your time before making a decision about immunisation. You don’t have to decide on the spot. You can always make another appointment, to ask more questions or to go ahead with the immunisation.

Find out more about immunisation by speaking with your health professional. The best place to start is with your GP. You can also ask your clinic nurse or specialist.

There is also lots of information online. If you would like to know more about immunisation, check out the Australian Government’s information on immunisation .

When looking for immunisation information, stick to reliable information providers, such as:

Where to get help

• Questions about vaccination , Department of Health, Australian Government.
• Australian Immunisation Handbook , Department of Health, Australian Government. 
• Immunisation schedule Victoria and vaccine eligibility criteria , Department of Health, Victorian Government.
• National Immunisation Program Schedule , Department of Health, Australian Government.
• Pre-immunisation checklist , Department of Health, Victorian Government.

Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional. The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular therapy, service, product or treatment described on the website is suitable in their circumstances. The State of Victoria and the Department of Health shall not bear any liability for reliance by any user on the materials contained on this website.