Vaccine. The word conjures up a host of emotions, from relief and hope to skepticism and even fear.

In truth, says Dr. Patrick Gavigan, a pediatric infectious disease physician at Penn State Children’s Hospital, vaccines are among the most heavily studied of all medical interventions, and the evidence shows they are safe and extremely effective. Many once-daunting diseases, such as measles, meningitis and pneumonia, have been combatted successfully with childhood vaccinations.

Most parents readily accept the vaccine schedule and bring their children for well-child visits expecting the vaccines will be given, Gavigan said. Those who hesitate often want clarification on things they have heard about vaccine safety or additives. Doctors understand there is misinformation and are happy to set the record straight.

“Most people with reservations about vaccines come to us with pretty good questions and are just looking for advice,” Gavigan said.

Here are a few of the most common myths about vaccines and reassuring truths.

• Vaccines can make you sick and cause the illness they’re supposed to prevent.

The truth: Vaccines contain inactive viruses or components of the virus or bacteria and cannot cause infection in people with normally functioning immune systems. “Common side effects, such as fever or pain at the injection site, that people often mistake for illness are the immune system’s response to the components and actually show the body is building immunity to the virus or bacteria,” Gavigan said. (People with compromised immune systems should consult their physician before taking any live virus vaccines.)

• Vaccines contain toxic ingredients.

The truth: Mercury and thimerosal, a mercury-containing organic compound, are no longer used in childhood vaccines or in many other vaccines. Safety data shows, however, that there was no increased risk of harm even when these compounds were present, Gavigan said.

• The choice not to vaccinate affects only my child, or only me.

The truth: Vaccines protect the person who gets vaccinated and build herd immunity by decreasing the prevalence of the virus to such low levels that people who are unable to get vaccinated or who don’t fully respond to the vaccine also are protected. A certain percentage of the population must be vaccinated to attain herd immunity, so a decision against vaccination affects the whole group, Gavigan said.

• Natural immunity is better than vaccine-acquired immunity.

The truth: While it may be true that someone who naturally catches a virus has longer-term immunity, the risks and consequences from actually getting sick with the infection far outweigh any value that may come from having the virus itself. “And with COVID-19, we don’t know that immunity from getting the infection is any better than the vaccine,” Gavigan said.

• It’s best to space out vaccines and even delay the COVID-19 vaccine until the pandemic is over.

The Truth: All of the data on a standard schedule for vaccines has shown them to be very safe. “Any time you space out vaccines, there’s a big risk that you’re providing additional time when you can contract the disease,” Gavigan said. In addition, getting multiple vaccines at the same time doesn’t diminish your immune system’s response to them, and there’s no need to worry that your body can’t withstand multiple vaccinations in short order. “The amount of antigen, or virus protein, in the vaccine is much lower than what you would encounter if you got the infection,” Gavigan said.

The COVID-19 vaccine has been developed and approved in short order, which makes people understandably concerned about its safety, Gavigan said.

“However, the data has been thoroughly looked at in tens of thousands of people involved in the studies, and the rates of adverse effects were exceedingly low,” he said. “This vaccine looks to be as safe and effective as we could hope for.”