VPD stands for vaccine-preventable disease, a term for any infectious illness that can be prevented or significantly reduced through vaccination. There are currently more than 20 diseases in this category, ranging from common infections like the flu to historically devastating ones like polio and smallpox. The concept matters because these diseases still kill and disable millions of people worldwide, despite the existence of safe, effective vaccines.
How Vaccines Prevent Disease
When you receive a vaccine, your immune system responds by creating specialized memory cells, both in the B cell system (which produces antibodies) and the T cell system (which destroys infected cells). These memory cells stick around long after the vaccination, some for decades. If the actual pathogen enters your body later, these cells recognize it and mount a response that’s faster and stronger than what your immune system could manage on its own the first time around.
The type of protection depends on the disease. For fast-acting threats like toxins or viruses that cause illness quickly, you need antibodies already circulating in your blood before exposure. For pathogens with longer incubation periods, your memory cells have time to ramp up a response after exposure. This is why some vaccines work by maintaining a steady level of protective antibodies, while others prime your immune system to react rapidly when needed.
The Full List of Vaccine-Preventable Diseases
The CDC’s current immunization schedules cover a wide range of diseases. For children and adults combined, vaccines are available for:
- Respiratory infections: influenza, COVID-19, RSV, pertussis (whooping cough), diphtheria, measles, mumps, rubella, pneumococcal disease
- Liver infections: hepatitis A and hepatitis B
- Neurological and systemic diseases: polio, tetanus, meningococcal disease, Hib (a bacterial infection that can cause meningitis in children)
- Viral infections: chickenpox, shingles, HPV, mpox
Some of these vaccines are given in childhood and provide lasting protection. Others require boosters throughout adulthood. Shingles and pneumococcal vaccines are specifically recommended for older adults, since the risk of severe complications from these diseases climbs sharply with age.
Why VPDs Still Matter
Vaccination is one of the most impactful public health interventions in history. Over the past 50 years, global immunization efforts have saved at least 154 million lives, the equivalent of six lives every minute of every year, according to a 2024 WHO analysis. The vast majority of those saved, 101 million, were infants.
The economic case is equally striking. CDC calculations show that every $1 spent on childhood immunizations saves approximately $11 in healthcare costs and lost productivity. That return comes from preventing hospitalizations, long-term disability, and the broader economic disruption that outbreaks cause.
Community Protection Thresholds
Vaccines don’t just protect the person who receives them. When enough people in a community are vaccinated, the pathogen can’t spread easily, which shields those who can’t be vaccinated, including newborns, people with weakened immune systems, and those with allergies to vaccine components. This is known as herd immunity.
The threshold varies by disease. Measles, one of the most contagious viruses known, requires about 95% of a population to be vaccinated before the remaining 5% are indirectly protected. Polio’s threshold is lower, around 80%. When vaccination rates drop below these levels, outbreaks follow quickly, and measles is typically the first signal because its threshold is so high.
VPDs Are Making a Comeback
Several vaccine-preventable diseases are resurging worldwide. Measles cases reached an estimated 10.3 million in 2023, a 20% increase over the previous year. In the 12 months leading up to April 2025, 138 countries reported measles cases, with 61 experiencing large or disruptive outbreaks. That’s the highest number in any 12-month period since 2019.
Measles isn’t the only concern. Meningitis cases in Africa rose sharply in 2024 and continued climbing into 2025, with more than 5,500 suspected cases and nearly 300 deaths reported in 22 countries during just the first three months of the year. Yellow fever is also increasing, with confirmed cases reported across multiple countries in Africa and the Americas. Diphtheria, a disease that had virtually disappeared in many countries, is now at risk of re-emerging.
Several forces are driving these outbreaks. The COVID-19 pandemic disrupted routine immunization programs globally, and coverage has not fully recovered. In 2023, an estimated 14.5 million children missed all of their routine vaccine doses, up from 12.9 million in 2019. More than half of these children live in countries facing conflict or instability. Meanwhile, misinformation about vaccines, rapid population growth, and cuts to global health funding are compounding the problem. A recent WHO survey found that nearly half of low- and lower-middle-income countries are experiencing moderate to severe disruptions to vaccination programs due to reduced donor funding.
Progress Toward Eradication
Polio offers a powerful example of what sustained vaccination can achieve, and how difficult the final stretch is. Wild poliovirus transmission is now confined to just two countries: Afghanistan and Pakistan. As of mid-2025, all new cases of wild poliovirus were reported from those two nations, with ongoing transmission concentrated in specific regional hotspots. The global target is to certify wild poliovirus eradication by 2027, though the WHO still classifies international spread as a public health emergency due to intense transmission in those remaining areas.
Smallpox remains the only human disease fully eradicated through vaccination, achieved in 1980 after a global campaign. Polio could eventually be the second, but the experience illustrates that eliminating the last pockets of a disease requires not just effective vaccines but stable healthcare infrastructure, political cooperation, and sustained funding.