What do measles, tuberculosis (TB), dengue, and malaria have in common? In addition to being some of the most deadly diseases facing humans today, they all can be prevented by vaccines.
Doctors Without Borders/Médecins Sans Frontières (MSF) vaccinates millions of people every year in our projects around the world. Although vaccines are a game-changing tool in the fight against preventable disease, not all people who need vaccines have adequate access to them.
The World Health Organization estimates that the lives of between 3. million and 5 million people are saved each year by vaccines. There are, however, an estimated 14.5 million “zero-dose” children, meaning those who have not received a single vaccine, and an addition 6.5 million children who are only partially vaccinated.

How do vaccines work?
Vaccines help the body recognize pathogens (including harmful bacteria, viruses, and parasites) so the immune system can begin to produce antibodies to effectively fight them off.
Vaccines can also reduce the severity and duration of a disease, even if someone still gets infected after vaccination. Someone may still get the disease, but it will be much less severe than if they hadn't been vaccinated.
Vaccines also protect the non-vaccinated. If enough people are vaccinated, a disease will no longer circulate in a community—this is called herd immunity. For example, outbreaks of measles and polio are extremely rare in countries with high vaccination coverage.
“Vaccines are extremely safe,” says John Johnson, a vaccination and epidemic response advisor at MSF. “When we look at safety in medicine, we look at risk versus benefit. Vaccines are kept to an extremely high standard of safety because we are giving them to people who aren't sick, so we can't accept side effects unless they are very minor or extremely rare. Among medical products, vaccines are some of the safest things we use.”
Meet our expert on vaccination
John Johnson

John Johnson is a vaccination and epidemic response advisor at the MSF France medical department. He has worked with MSF on Ebola outbreak response in Monrovia, Liberia, and in North Kivu, DRC, where he was project lead for an Ebola vaccine trial. He currently sits on the International Coordinating Group for Ebola vaccine provision and is co-chair of the Ebola vaccine coordination team (EVCT) technical and programmatic guidance working group. He holds a master's degree in nursing and a diploma in vaccinology.
Why are vaccines essential for public health?
An ounce of prevention is worth a pound of cure, so the saying goes. A common-sense preventative measure like vaccination can spare people from getting sick, and the sometimes arduous process of healing.
Vaccines are effective on an individual scale to help people avoid getting sick, but societies as a whole benefit from vaccines in several ways:
- Vaccines keep people out of hospitals, helping them function more smoothly and prevent being overwhelmed during an epidemic.
- Vaccines also help prevent many diseases for which there are no specific drugs for treatment, such as measles, polio, rubella, hepatitis B, rabies, rotavirus, and HPV.
- Vaccines reduce use of antibiotics, which helps prevent antimicrobial resistance.
“Vaccines are one of the most important public health interventions ever,” says Johnson. “They are right up there with clean water and sanitation in terms of improving health and saving lives.”

Why are childhood vaccinations so important?
Children are especially vulnerable to infectious diseases, because they don't have the same understanding of how diseases are spread. “Babies put everything in their mouth during the first year or two of life, and younger kids don't necessarily know how to wash their hands, for example, says Johnson.
Children are at higher risk of developing more severe cases and infections than adults because they are building up their immunity in the first few years of life. Although children are born with maternal antibodies that protect them from several diseases in the first few months after birth, this protection wanes and they become more vulnerable to infection and disease.
What are the main barriers to vaccination?
Conflict, lack of infrastructure, and living in hard-to-reach areas are among the reasons millions of people are unable to obtain vaccinations. Reaching these people, mostly children, requires enormous efforts to transport and deliver vaccines to end users, while maintaining them proper conditions.
Disease in the wake of conflict
The interruption of vaccine access has swift negative consequences. Among our current projects, MSF has witnessed the following:
- Measles cases are increasing in the Darfur region of Sudan due to the interruption of routine activities by the ongoing conflict.
- Palestinians in Gaza were a well-vaccinated population until the beginning of war in October 2023. After less than a year of vaccine interruption, the first case of polio in 25 years was recorded in Gaza.
- Northern Nigeria has seen the reemergence of diphtheria due to low vaccination coverage, which has been fueled in part by insecurity in the region.
- North Kivu province in Democratic Republic of Congo (DRC), where fighting has intensified over the past two years, is seeing measles outbreaks.
- Yemen, where conflict is ongoing, is experiencing regular cholera and measles outbreaks.

Why are vaccines difficult to deliver to people in remote areas?
Vaccines need to be kept cold when being transported and stored in order to remain effective. This is a particularly daunting challenge in areas with high temperatures and no direct routes to reach communities.
When there is no direct route, health care providers have to find creative solutions. Over a 37-day campaign in DRC, MSF used boats and motorcycles to transport vaccines in coolers to remote areas in the Maniema region, where we vaccinated 60,000 children against measles. More than 2,000 children under 2 years old were also vaccinated against pneumonia.
How does cost and supply affect vaccination?
Ten years ago, it cost countries less than $1.50 to buy the main recommended vaccines to protect a child’s life. Today, the lowest price for the recommended vaccination package is nearly $40. That’s because not only are more vaccines now included in immunization programs, but many new vaccines cost much more than older ones.
There are also global shortages of some vaccines. Currently, only one company manufactures a cholera vaccine as global demand is soaring amid multiple simultaneous outbreaks, including in South Sudan, Sudan, Zimbabwe, and Yemen.
MSF has called for existing manufacturers to scale up vaccine production, and that the efforts of new manufacturers be supported.

How is MSF responding to vaccination needs around the world?
MSF prioritizes vaccination as a core health service. We focus on responding to outbreaks, boosting preventive vaccination in our pediatric and emergency projects, investing in research on ways to better utilize current vaccines, and advocating for cheaper vaccines that are better-adapted to tropical climates and low-resource settings.
Sudan
In addition to creating the world’s largest displacement crisis that has uprooted more than 9 million people, the war in Sudan has wreaked havoc on access to health care for people affected by the conflict. MSF recently vaccinated nearly 10,000 children for measles in central Darfur between June and October 2024, after 1,000 children, mostly under 5 years old, contracted the disease.
Ethiopia
More than 7.3 million malaria cases were reported in Ethiopia in 2024, according to the World Health Organization (WHO)—nearly twice as many as in 2023. Years of insecurity and limited access to health care have left people increasingly vulnerable to malaria in the Oromia region, which accounts for nearly half of all cases in the country.
MSF’s efforts are focused on preventing, treating, and controlling the mosquito-borne disease in the regions’ most vulnerable communities, including refugees and internally displaced people.
A recent MSF vaccination campaign in collaboration with the Ministry of Health, administered three doses of the R21 measles vaccine to 2,750 children, with a fourth dose due to be administered after 12 months.
South Sudan
A mass vaccination and treatment campaign in Twic County, South Sudan, resulted in significant reduction in malaria cases, especially among vulnerable children. By the end of October 2024, the team reached a total of 18,700 children.
Malaria is a leading cause of illness and death among children in South Sudan. The country faces malaria outbreaks every year, which have worsened due to factors such as flooding, poverty, and a fragile health system. Despite the predictable recurrence of malaria peaks, immunization coverage remains inadequate, contributing to overcrowded health facilities and an unbroken cycle of severe cases.