Virologist Viewpoints: The Positive Side Effects of Vaccines

Public debate over vaccines can be traced back centuries and continues at full force today. Fear and mistrust often dominate the conversation, with scientific evidence lost in the noise. 

But as health officials become increasingly concerned about declining vaccination rates—especially after a child in Texas died from measles, marking the first such death in a decade—scientists are speaking out to inform and educate the public.  

I am one of those scientists. I want people to know that vaccines are not just tools for preventing infections—they’re pillars of global health, and they offer individual and societal benefits that extend far beyond their original purpose. They save lives, reduce suffering, and build resilience against both current and future health challenges.

If people can learn more about the wide range of benefits provided by vaccines, it may be easier for them to embrace vaccines without fear. Here are six things everyone should know about vaccines: 

1. Vaccines are so effective that they make us forget how deadly viruses can be. 

At their core, vaccines are designed to prevent disease, and they do this remarkably well. Vaccination campaigns have saved millions of lives by reducing disease and death from infectious diseases. 

Consider the case of measles, one of the world’s most contagious diseases. Measles is a dangerous virus that infects the brain and can lead to fatal brain swelling. 

Before the vaccine, the virus killed an estimated 2.6 million people every year. Since a vaccine became available in 1963, widespread immunization brought that number down by more than 90 percent. And, measles was declared eliminated in the U.S. in 2000.

2. Vaccination protects communities from outbreaks.

Not only is vaccination the most effective way to protect children and adults from getting infected by a virus; it’s also the best tool to stop viruses from spreading across entire communities.

In general, we need a 95 percent vaccination rate to protect communities against the spread of a virus. This is something called herd immunity, meaning that if enough people are vaccinated, the whole community is protected. 

In many counties in Texas where new cases of measles are being reported, the vaccination rate among kindergarteners is well below this threshold, making those places particularly vulnerable to the virus.

3. Vaccine protection often extends beyond the indicated disease.

Several vaccines offer protection beyond their primary targets. 

The measles vaccine indirectly strengthens overall immune function. Measles infections cause “immune amnesia,” in which the immune system basically forgets how to mount an effective defense against any virus. Immunity is weakened for months or years, and the body becomes more vulnerable to other infections. Vaccination prevents this, so it reduces mortality from diseases, such as pneumonia and diarrhea.

The BCG (Bacille Calmette-Guérin) vaccine, developed for tuberculosis, drastically reduces overall death in children—not just from tuberculosis. This effect is attributed to “trained immunity,” where the innate immune system becomes more effective at responding to other infections after vaccination. Remarkably, this benefit extends to cancer. The BCG vaccine is now a recognized treatment for bladder cancer, likely due to its positive effect on immune health.

4. Vaccines can lower the risk of Alzheimer’s disease.

Vaccines have been shown to reduce the risk of neurodegenerative diseases, such as Alzheimer’s and dementia, by lowering systemic inflammation and protecting against infections linked to cognitive decline.

Multiple studies have confirmed dementia-protective effects of vaccines. For example, people over 60 who received at least one influenza vaccine were 40 percent less likely to develop Alzheimer’s over the next six years than those who were not vaccinated. The protective effect was stronger when the vaccine was received annually, suggesting a cumulative benefit from regular vaccination.

A similar effect was detected in people who received the shingles vaccine, who had a 20–30 percent reduced risk of dementia. This is particularly interesting given that infection with herpes viruses such as varicella zoster, the virus that causes chickenpox and shingles, has been directly linked to Alzheimer’s disease. The vaccine prevents the virus from flaring up, but it may also reduce overall inflammation, which is an emerging driver of neurodegeneration.

Also, research in people treated with the BCG vaccine for bladder cancer showed a 20 percent lower occurrence of Alzheimer’s disease than unvaccinated people, showing the vaccine’s ability to control chronic inflammation.

5. Vaccines address antibiotic resistance, a growing public health concern.

More than 39 million people around the world are predicted to die from antibiotic-resistant infections over the next 25 years.

The pneumococcal vaccine, for instance, prevents bacterial infections, such as pneumonia, and directly suppresses the emergence and spread of resistant microbes. By reducing the number of people falling sick, the vaccine also counters the overuse of antibiotics and indirectly lowers the risk for resistance emergence.

Widespread use of pneumococcal and rotavirus vaccines in children is estimated to avert 11.4 million days of antibiotic use annually worldwide.

6. Vaccination has broad economic benefits.

At a basic level, vaccines prevent adults from missing work due to illness and reduce the long-term economic impact of vaccine-preventable diseases that can cause disability.

Globally, every $1 spent on vaccines generates $44 in economic benefits, according to estimates by the World Health Organization—factoring in healthcare savings, increased productivity, and reduced disease burden. Since it was introduced in the 1950s, the polio vaccine alone has saved an estimated $27 billion in treatment costs.

This article is written by Melanie Ott, MD, PhD, a virus expert and director of the Gladstone Institute of Virology.