A Vaccine Q&A

Vaccines continue to be in the news lately, and some potentially misleading information is being shared by individuals who may not have medical training or expertise. We have put this Q&A together to provide some clarity on a topic that should no longer be controversial.

What Are Vaccines?

Vaccines help the body build immunity to disease. Unlike medications, which treat an illness, vaccines prevent disease or lessen its impact. Some vaccines are given as injections. Others are administered as a liquid, pill, or nasal spray. Designed to mimic a disease-causing microorganism, vaccines train the immune system to recognize a specific disease-causing bacteria, virus or other pathogen. This “memory” can provide years, or even a lifetime of disease prevention.

How Do Vaccines Work?

Vaccines contain antigens, substances that cause the immune system to begin producing antibodies. The antigens in vaccines trigger your body’s immune response. In order to fight infection, white blood cells create antibodies, proteins whose job it is to identify and destroy foreign substances. Along with antibodies, your immune system makes memory cells that "remember" the specific antigen. Once these memory cells are created, you are effectively immunized. If you are ever exposed to a pathogen against which you have been vaccinated, your body is trained to wage a rapid, robust response.

What Are the Benefits of Vaccines?

The primary benefit of vaccines is to prevent disease in a vaccinated person. Even if a person does contract the disease, the severity and risk of complications is greatly diminished. Some vaccines, such as the human papillomavirus, or HPV vaccine, prevent certain cancers. Vaccines also help protect others. When most people in a community are vaccinated, there are fewer people around to spread infection, protecting people who can’t be vaccinated, such as newborns, immunocompromised individuals, or cancer patients. Lastly, global vaccination can eradicate specific diseases, such as smallpox. Polio, while not totally eradicated, has also become quite rare thanks to vaccination.

What Types of Vaccines Are There?

Different types of vaccines use different types of antigens:

• Inactivated antigens contain dead virus or bacteria such as Polio or Hepatitis A.
• Live attenuated antigens use a weakened pathogen – one such vaccine is MMR, which protects children from measles, mumps, and rubella.
• Antigens for Subunit, Recombinant, and Polysaccharide vaccines such as HPV or Hepatitis B use parts of an infectious microorganism.
• The Antigens in toxoid vaccines such as the Tetanus and Diphtheria vaccine come from a toxin produced by a bacterium – the toxin is rendered harmless through heat or chemicals.
• mRNA vaccines do not contain an antigen. Instead, they use messenger RNA which trains your cells to make the needed antigen. The Pfizer and Moderna COVID-19 vaccines are an example of this type of vaccine.
• Viral Vector vaccines like the one used to immunize people against Ebola use a harmless modified virus to deliver genetic instructions.

Can you still get infected by a disease you’ve been vaccinated against?

If you are exposed to a disease immediately following a vaccine against it, you can still become infected. However, a vaccinated person is much less likely to become seriously ill or die from a disease than an unvaccinated person whose immune system is not prepared to fight the pathogen.

Why do some vaccines need boosters while others don’t?

The number of doses needed to achieve immunity depends on whether the antigen in a vaccine is live-attenuated. Because they contain living bacteria or viruses, live-attenuated vaccines such as the chicken pox or combined measles, mumps, and rubella (MMR) only need two doses to provide lasting, even life-long protection. Most non-live vaccines, such as the combined vaccine for diphtheria, tetanus, and whooping cough (DTaP) require at least three doses to achieve protection that fades over time and eventually require a booster. Vaccines such as those for COVID or the flu are reformulated and readministered regularly to keep up with mutation-prone viruses that cause seasonal waves of infection.

How are vaccines approved?

Vaccine ideas are first tested in a research lab, using cells. If the results show promise, the next step is animal testing. From there, vaccines are tested in clinical trials using human volunteers. This is typically a 3-phase process:

1. The formula is tested on 20-100 healthy volunteers to look for side effects and fine tune the dosage.
2. The vaccine is tested on several volunteers to evaluate the strength of the immune response and again, look for side effects.
3. The vaccine is tested on thousands of people from diverse populations to determine whether the vaccine is safe and effective for large-scale use. If a formula proves to be effective and the side effects are minimal, the vaccine is submitted for approval by the U.S. Food and Drug Administration (FDA). As part of the approval process, the FDA evaluates the research and clinical trials, the manufacturer and the manufacturing process. The vaccine may be approved at one of two levels. BLA (Biologics License Application) is full approval. EUA (Emergency Use Authorization) is approved only for public health emergencies. Once a vaccine is approved, production must meet strict quality standards. Each batch is tested for consistency, efficacy, and contamination, and facilities are inspected regularly.

Do vaccines have side effects?

The side effects you may feel after vaccination are generally caused by your own immune system as opposed to the vaccine itself. While unpleasant, side effects are an indication that the vaccine has done its job and your immune system is revved up. Potential side effects include:

• Soreness, redness, swelling, or warmth at the injection site
• Flu-like symptoms such as low-grade fever, fatigue, headache, chills, nausea, muscle pain, or sore joints
• Less common reactions such as dizziness, swollen lymph nodes, and/or a mild rash
• Rare but serious reactions include severe pain and swelling in the vaccinated arm and allergic reactions such as rash and difficulty breathing (anaphylaxis). These can be serious and require a trip to the Emergency Department or Urgent Care.

Do Vaccines Cause Autism?

In a word, no. This persistent rumor was sparked by a study based on falsified data. Its author, Andrew Wakefield, lost his medical license over this fraudulent study. The theory that vaccines cause autism has been debunked through extensive scientific research.

What is a vaccine schedule?

The Advisory Committee on Immunization Practices (ACIP) develops recommended vaccine schedules for the population at large, starting from birth. Timing matters. Babies and young children should be vaccinated when their immune systems are ready and they are less likely to be exposed to pathogens. Routine vaccines are given throughout infancy and childhood. Teens may get boosters and the HPV vaccine, which protects against certain cancers caused by exposure to the HPV virus. Adults need boosters for childhood immunizations, such as TDAP, over time. Annual Flu shots are a good idea for all adults. Older adults should also be vaccinated against shingles and pneumonia. If you are planning to travel abroad, some countries require vaccines for yellow fever, typhoid, hepatitis A/B and other diseases.

What vaccines do I need? What about my children?

It is recommended that most individuals 6 months of age or older get a yearly flu shot – and now is the perfect time. Other vaccine recommendations – particularly for COVID – have changed in the past few weeks. Talk to your doctor or your child’s pediatrician to see which immunizations you need to protect the health or you and your loved ones. And remember, all currently available vaccines have been thoroughly tested and proven to be safe and effective.

Speak with a doctor to determine which vaccines are right for you and your family. For help finding a doctor, click here.

This article first appeared in the September 2025 edition of the HealthPerks newsletter.