Are Vaccines Safe? Common Myths and Facts Explained

文章作者: Dr Ooi Poh Siang, Family Medicine Specialist

03 April 2026

Vaccine Myths vs Facts: What You Should Really Know

one dose of vaccine

Vaccines are one of the most effective ways to prevent serious diseases. However, many people still have concerns or misunderstandings about vaccines, especially with the amount of information shared online. Here are some common vaccine myths — and the facts you should know.

Myth 1: “I am healthy, I don’t need vaccines”

Fact: Even healthy individuals can get infected and develop complications. Vaccines are not only for people who are sick — they are meant to prevent illness before it happens.

For example:

Influenza can cause severe illness even in young adults
Dengue can lead to bleeding and hospitalisation
RSV (Respiratory Syncytial Virus) can affect previously healthy individuals

Vaccination also helps protect people around you, including children, elderly parents, and those with weaker immune systems.

Myth 2: “Too many vaccines will weaken the immune system”

Fact: Vaccines do not weaken the immune system — they train it. Every day, our immune system is exposed to hundreds of germs from food, air, and the environment. Vaccines only introduce a small, controlled amount of antigen, allowing the body to build protection safely.

In fact, vaccines:

Strengthen immune memory
Help the body respond faster to real infections
Reduce the risk of severe disease

Myth 3: “The flu vaccine can cause flu”

Fact: The flu vaccine cannot cause influenza infection. Most flu vaccines contain inactivated (killed) virus or only parts of the virus, which cannot cause disease.

Some people may experience:

Mild fever
Body aches

This is a normal immune response, not an infection.

Myth 4: “Vaccines are not safe during pregnancy”

Fact: Some vaccines are safe and strongly recommended during pregnancy.

Examples include:

Influenza vaccine
Tdap vaccine (Tetanus, Diphtheria, Pertussis)

These vaccines help protect both the mother and the baby (through transfer of antibodies). However, certain vaccines (such as live vaccines like varicella) are not given during pregnancy, which is why it is important to consult a doctor.

Myth 5: “Natural infection is better than vaccination”

Fact: Getting infected carries much higher risks than vaccination. While natural infection can lead to immunity, it may also cause severe illness, long‑term complications, hospitalisation or death.

Examples:

Chickenpox → pneumonia, brain infection
HPV (Human Papillomavirus) → cervical cancer
Hepatitis B → liver cirrhosis and liver cancer

Vaccines provide safe and controlled protection without these risks.

Myth 6: “Vaccines are only for children”

Fact: Vaccination is important throughout life. Adults and elderly individuals may actually have higher risk of complications due to weaker immunity.

Examples of important adult vaccines:

Influenza (yearly)
Pneumococcal
Shingles
Tdap booster

Vaccination should be viewed as a lifelong health strategy.

Myth 7: “If I missed vaccines earlier, it’s too late”

Fact: It is never too late to catch up. Many vaccines can still be given in adulthood.

Examples:

HPV vaccine
Hepatitis B vaccine
Tdap booster

Your doctor can help create a catch‑up vaccination plan.

Myth 8: “Vaccines have many serious side effects”

Fact: Most vaccines have mild and temporary side effects.

Common side effects:

Pain at injection site
Mild fever
Fatigue

Serious side effects are very rare, and vaccines are carefully tested for safety before approval. The risk of complications from the disease is much higher than from the vaccine.

Myth 9: “I don’t travel, so I don’t need extra vaccines”

Fact: Some infections are common locally, not just overseas.

For example:

Dengue is endemic in Malaysia
Influenza circulates yearly
Hepatitis A can be transmitted through food

Travel vaccines are important, but local protection is equally important.

Myth 10: “I cannot take more than 1 vaccine in a single visit”

Fact: It is safe and recommended to receive multiple vaccines during the same visit.

Why?

Your immune system can handle multiple vaccines at once
This reduces missed opportunities for protection
Fewer clinic visits = more convenient and better compliance

Example:

An elderly person may receive influenza + pneumococcal vaccines during a single visit.
A traveller may receive hepatitis A + typhoid vaccines in one visit safely.

Myth 11: “HPV (Human Papillomavirus) vaccine is only for those who are sexually active”

Fact: The HPV vaccine is most effective before exposure, which is why it is recommended before sexual activity begins.

Why?

Human papillomavirus spreads through skin‑to‑skin sexual contact
The vaccine prevents infection, not treats it
Early vaccination gives stronger and longer‑lasting protection

The vaccine is for prevention, not treatment.

Myth 12: “Vaccines contain harmful substances like aluminium and thiomersal”

Fact: These ingredients are used in very small, safe amounts and have been extensively studied.

Breakdown:

Aluminium (adjuvant) – Helps your immune system respond better. The amount is much lower than what we get from food and water daily. An infant receives only about 4.4 mg of aluminium salts from vaccines, compared to about 7 mg from breast milk over 6 months.
Thiomersal (preservative) – Prevents contamination in multi‑dose vials. Single‑dose vials do not contain thiomersal. It contains a form of mercury (ethylmercury) that is quickly cleared from the body. It is different from methylmercury (the type found in fish and known to be harmful in high amounts). Not linked to autism or long‑term harm.

Vaccines undergo strict safety monitoring worldwide before approval.

Key Takeaway

Vaccines are safe, effective, and essential for protecting your health at every stage of life. Misinformation can lead to unnecessary fear, but understanding the facts helps you make informed decisions for yourself and your family. If you are unsure about which vaccines you need, speak to your doctor for personalised advice.