The question of whether current childhood vaccines are safer than the diseases they prevent continues to spark debate, despite the answer being as close to “settled science” as any. And although many once-prevalent illnesses like polio, mumps, and diphtheria have been largely eradicated in the United States, vaccines remain essential to maintain this protection.
Proof of that can be found currently in deep-red, under-vaccinated western Texas, where, by March 28, an ongoing outbreak of measles had grown to at least 400 cases, plus another 120-plus in other states. In Texas alone, 41 patients had been hospitalized, and a 6-year-old child died. Virtually all the cases were in unvaccinated individuals or individuals whose vaccination status was unknown.
Population immunity, also known as herd immunity, occurs when a community is protected from an infectious disease because enough people in the community are immune. Immunity can result from vaccination or from having had the infection previously. Because of vaccination, the probability of encountering measles, rubella, or polio in the U.S. is low since widespread vaccination has built protective barriers. But if vaccinations decline, these diseases can rapidly resurface, as in the current measles outbreak in Texas and other states.
Moreover, vaccines protect not only those who receive them but also the most vulnerable members of society — infants too young to get the vaccines and people who are immunocompromised. By getting vaccinated, children and adults contribute to a community-wide barrier that prevents the spread of pathogens.
The safety and effectiveness of vaccines are best understood by comparing the risks of the diseases they prevent versus the risks associated with the vaccines themselves.
For instance, if 10,000 children were to contract measles, the expected complications would include:
• 2,000 hospitalizations
• 10 cases of brain swelling
• 10–30 deaths of children
• 1,000 ear infections with potential permanent hearing loss
• 500 cases of pneumonia
In contrast, if 10,000 children receive the MMR (measles, mumps, rubella) vaccine, statistically, the expected side effects would be:
• 3 cases of fever-related seizures
• 0–1 cases of abnormal blood clotting
• 0.035 cases of severe allergic reactions
These numbers highlight the dramatic difference in risk between contracting a disease and receiving a vaccine. The complications of preventable infectious diseases can be severe or even fatal, while serious side effects from the vaccines are extremely rare.
The FDA performs a rigorous review of laboratory, preclinical (animal testing), and clinical data to ensure the safety, efficacy, purity, and potency of vaccines. After they are approved for marketing, vaccines may be required to undergo additional studies to address specific questions. Because vaccines are administered to large numbers of healthy people to prevent infections, they are subjected to especially rigorous oversight.
Vaccine safety is also monitored through several systems that allow patients to report side effects or enable researchers to study medical records for safety concerns:
• Vaccine Adverse Event Reporting System (VAERS): Anyone can report a possible vaccine reaction, but these reports require thorough follow-up to determine causation.
• Vaccine Safety Datalink (VSD): A network of medical records that allows researchers to study possible vaccine-related safety concerns in large populations.
• V-safe: A recently introduced program that enables vaccine recipients to provide real-time feedback via text messaging to the Centers for Disease Control and Prevention (CDC) about any side effects they experience.
It is true that children today receive more vaccines than previous generations, but that is often misinterpreted. It does not imply that they are at greater risk. Scientific advances have led to vaccines that are more targeted, efficient, and safe. In the 1980s, vaccines exposed children to over 3,000 antigens (the part of the vaccine that elicits an immune response); today, despite protecting against more infectious agents, childhood vaccines contain only about 180 antigens. In any case, this level of exposures is far less than to the microorganisms that children encounter in everyday life.
Vaccines have dramatically reduced rates of severe childhood illnesses. For example, the introduction of the Haemophilus influenzae type b (Hib) vaccine in the late 1980s significantly decreased cases of childhood meningitis, pneumonia, and epiglottitis.
And this chart shows the number of cases per 100,000 people before and after the introduction of the measles vaccine.
Courtesy of Global Center for Health Security, Nebraska Medical Center.
Similar successes have been observed with vaccines against many other viruses and bacteria, including the complete elimination from the U.S. of endemic cases of diphtheria, polio, and smallpox.
For certain diseases like pertussis (whooping cough) and tetanus, booster shots are necessary to maintain immunity. They serve two main purposes: to reinforce immunity that wanes over time and to counteract genetic changes in pathogens that could make them resistant to vaccines.
A deluge of misinformation has led to unwarranted fears about vaccines, but the data overwhelmingly support their safety and effectiveness. The risks of vaccine-preventable diseases far outweigh the minimal risks associated with vaccination. Moreover, rigorous monitoring of side effects ensures that vaccines remain among the safest medical interventions available.
By maintaining high vaccination rates, we not only safeguard individual health but also preserve the collective health of our communities, ensuring that preventable infectious diseases remain a thing of the past. However, vaccine regulatory reviews, approvals, and uptake may be approaching difficult times. The FDA's top vaccine official, Dr. Peter Marks, the highly regarded director of the Center for Biologics Evaluation and Review, resigned under pressure on March 28. He said that HHS Secretary Robert F. Kennedy Jr.’s aggressive antagonism towards vaccines was irresponsible and posed a danger to the public. “It has become clear that truth and transparency are not desired by the secretary, but rather he wishes subservient confirmation of his misinformation and lies,” Dr. Marks wrote to Dr. Sara Brenner, the agency’s acting commissioner. As a former research virologist and a 15-year veteran of the FDA myself, I agree with Dr. Marks' assessment.
Henry I. Miller, MS, MD
Henry I. Miller, MS, MD, is the Glenn Swogger Distinguished Fellow at the American Council on Science and Health. His research focuses on public policy toward science, technology, and medicine, encompassing a number of areas, including pharmaceutical development, genetic engineering, models for regulatory reform, precision medicine, and the emergence of new viral diseases. Dr. Miller served for fifteen years at the US Food and Drug Administration (FDA) in a number of posts, including as the founding director of the Office of Biotechnology.
