Global Immunization: Vaccine Coverage is Variable

Vaccine availability

Vaccines may not be readily available due to:

  • Lack of supply
  • Failure of the healthcare system
  • Social barriers — Hard-to-reach groups can result from cultural, language, ethnic or geographic circumstances

Personal beliefs

Individuals or groups may have beliefs that make them unwilling to get vaccines:

  • Anthroposophical beliefs — These beliefs are based on the idea that being naturally exposed to common illnesses makes the immune system stronger.
  • Religious beliefs — These beliefs may be based on the idea that disease is an “act of God.” In other cases the objection is to putting certain things into one’s body.

Vaccine safety concerns

If you have heard of a vaccine safety concern and you do not see it discussed here, please contact us through e-mail at

Some people suffer an adverse event, or negative consequence, after receiving a vaccine. These events can be causal or coincidental.

  • Causal events are those negative consequences that are a direct result of having received the vaccine, either because of the vaccine or its administration.
  • Coincidental events are negative events that follow vaccine administration but which were not caused by the vaccine. Because of their coincidental timing, these unrelated events may be thought of as a consequence and may lead to decreased acceptance or use of the vaccine.

Distrust of authority may also lead to decreased use of vaccines if people believe that vaccines are meant to harm rather than help them. Misinformation also contributes to vaccine safety concerns.

Each of these sources of concern is discussed below.

Adverse events specific to certain vaccines

Paralysis after polio vaccine

There are two types of polio vaccines. The inactivated polio vaccine (IPV), also known as the Salk vaccine, is given as a shot. The other is a live polio vaccine (OPV), known as the Sabin vaccine; it is given orally. Both are used in different parts of the world; however, one can cause rare cases of paralysis as a side effect. To understand the differences between the vaccines, it is important to understand how the virus works.

Polio typically enters the mouth, multiplies in the intestine and is excreted in the feces. While in the intestinal tract, the virus enters the bloodstream and can infect the central nervous system. Most people who get polio don’t know they are infected. Some have mild flu-like symptoms. An even smaller number get meningitis or paralysis. Meningitis and paralysis occur when poliovirus infects the central nervous system.

The basis for the differences between the two vaccines lies in how they are made and how they are given:

  • IPV — The inactivated polio vaccine is made from poliovirus that has been treated chemically so that it cannot reproduce or cause disease. Additionally, since the vaccine is given as a shot, the virus never goes to the intestine and is, therefore, not excreted in feces.
  • OPV — The oral polio vaccine is made from live, weakened poliovirus. Giving the vaccine by mouth and as a live, weakened virus means that the virus will reproduce itself in the intestinal tract and the central nervous system, the virus may be excreted in feces, and in rare cases (1 in every 2.4 million doses), the vaccine can cause paralysis.

The OPV vaccine, despite causing rare cases of paralysis, was used for many years in the U.S. and is still used in many other places around the world. There are a few reasons for this:

  • Better protection — In places where there is still a significant threat of polio infection, the OPV vaccine provides better protection because the virus reproduces itself in the gastrointestinal tract and induces intestinal immunity. This vaccine was therefore better able to eliminate shedding of virus from the intestines and spread to other people. Additionally, because the virus replicates in the gastrointestinal tract, others are exposed to the vaccine virus and may become immune; this is referred to as contact immunity.
  • Better herd immunity — Because people who were immunized sometimes excrete virus in their feces, others around them can be exposed to the vaccine virus and become protected.
  • More cost effective — When resources are limited, OPV is more cost effective because it is given by mouth not needle, so it’s easier to administer.

The U.S. used OPV exclusively between 1963 and 1996. Once polio in this country was controlled, the recommendation was changed to use IPV.

Brain damage after Japanese encephalitis virus (JE) vaccine

Most people who are infected with JE do not know they have it; however, symptomatic disease is characterized by high fever, change in mental state, abdominal pain, diarrhea, headache and eventual disturbances in speech, gait, or other motor dysfunction. The disease is spread by mosquitoes and is more common in regions of southern Asia, such as Japan, Korea and China.

The most commonly used JE vaccine is made in mouse brain cells and then chemically treated, so that it cannot cause infection. The vaccine can cause side effects. For example, 1 in 5 people who get the vaccine experience headaches, muscle aches and malaise, and about 1 in 100 people experience redness, swelling or a lump at the injection site. Sometimes, the vaccine also causes more severe allergic reactions, such as rash and swelling of the extremities, face or throat and can lead to respiratory distress. This can occur in about 2 to 6 people per 1,000 who receive the vaccine.

A more severe reaction, known as encephalomyelitis, which is a swelling of the brain and spinal cord, has also been observed. A well-controlled study from Denmark found that in about 1 in every 50,000 to 75,000 doses, encephalomyelitis may occur; however, these data were not reproduced in the U.S. and Japan where rates were found to be about 1 in every 500,000 doses.

Because of the high rate of adverse events and the low level of disease, many countries do not commonly recommend this vaccine. However, the vaccine is recommended in areas where the risk of disease is higher.

Uncontrollable crying and brain injuries after pertussis vaccine

When the pertussis vaccine was first made, it contained all of the pertussis bacterial proteins. This first version of the vaccine is referred to as the whole-cell pertussis vaccine and results in fever and redness, swelling and pain at the injection site in about 1 of every 2 patients who receive it. High fever (105°F) and uncontrollable crying are also common, occurring in about 1 and 4 of every 100 persons, respectively. A newer version of the vaccine, called the acellular pertussis vaccine, contains fewer pertussis proteins and causes fewer reactions. While some countries, including the U.S., use the acellular version, many countries still use the more economical whole-cell version.

The whole-cell pertussis vaccine was suggested as a cause of brain injury including epilepsy and intellectual disabilities; however, multiple studies have found that while there are more cases of fever-induced seizures, there are not permanent brain injuries. The vaccine has also been questioned with regard to infantile spasms and SIDS. Neither was found to be causally related to the whole-cell pertussis vaccine.

Adverse events due to administration or program issues

Contaminated vaccines

Vaccines can be supplied in either single- or multi-dose vials. When multiple doses are contained in a vial, each time another dose is given, a needle is inserted into the rubber stopper that seals the vial. Unfortunately, if the needle becomes contaminated, the contaminating agent can enter the vial leading to contamination of future doses of vaccine taken from that vial. Contaminated doses can lead to abscesses at the injection site.

To reduce these occurrences, manufacturers have made more vaccines available in single dose vials and have started to supply some in special syringes; however, these measures make vaccines more expensive as well as increase the amount of storage space needed to keep the vaccines in appropriate temperature conditions. In developing countries, where resources are limited, multi-dose vials are still commonly used. To prevent contamination, preservatives, which kill contaminating bacteria and fungi, are used in multi-dose vials.

Proper handling and disposal of syringes

Sometimes needles and syringes have been reused or not discarded properly. In these instances, blood-borne diseases, such as hepatitis A, hepatitis B and HIV, can be spread.

UNICEF and other programs that support immunizations have started to provide needles that can be used only once in order to reduce this occurrence.

Vaccine stability

Vaccines must be kept at certain temperatures and used by certain expiry dates. This is fairly easy to do in developed countries; however, in the developing world this is much more difficult. If a vaccine is not stored properly or used by a certain date, it may not work.

For vaccines used in developing countries, manufacturers have designed vial labels that show whether a vaccine was stored properly. Recording temperatures of storage equipment and rotating stock help avoid these issues as well.

Manufacturing issues

In some cases, issues arise during vaccine manufacture. While this doesn’t happen often, it occurs occasionally. Typically, safeguards in place within the manufacturing process allow these issues to be detected before anyone ever receives the vaccine, but once in a while the vaccine gets distributed without knowledge of a problem.

Vaccines that are too dilute, too concentrated, or otherwise not prepared appropriately is one example. In one of history’s most horrible vaccine disasters, known as the Cutter Incident, 70,000 people in the U.S. got polio, 200 people were paralyzed, and 10 were killed because vaccine virus was not properly killed. This event occurred in 1955, when the polio vaccine program was new and led to added regulation and oversight of the vaccine industry in the U.S.

Contaminated preparations can also be of concern. For example, early in 2009, health officials in the U.K. had to withdraw doses of meningitis C vaccine, typically given to all 4-month-old infants, because of contamination with another type of bacteria. Fortunately, no one was reported to have suffered adverse events from this error. These events are obviously extremely rare.

Coincidental timing

Several diseases with onset or diagnosis sometime after receipt of vaccine have been suggested as being caused by vaccines. Some of these have included SIDS, multiple sclerosis, diabetes, neurological delays, arthritis and autism. All of the studies designed to determine whether vaccines caused any of these problems have found that vaccines don’t cause chronic disorders.

Distrust of authority

Vaccines cause infertility

Several vaccines have been accused of causing infertility. These unsubstantiated claims have been made primarily in the developing world where there is concern about the goals of the U.S. and other western cultures during immunization campaigns.

Polio and tetanus vaccines were claimed to contain a protein common in pregnancy, called human chorionic gonadotrophin or hCG. Tests of the vaccine lots disproved this claim.

Anthrax vaccine was suggested to decrease semen count in men and cause miscarriages in women; however, studies of military personnel have not substantiated these claims.

Finally, the HPV vaccine has been implicated in infertility because it contains polysorbate 80 as a stabilizer. However, the amount of polysorbate 80 in the vaccine is very small. Each dose contains 50 micrograms (a microgram is one-millionth of a gram and a gram is the weight of one-fifth of a teaspoon of water). To put this in perspective, polysorbate 80 has been used for many years as an emulsifier to make ice cream smooth and to slow melting. A typical serving of ice cream (1/2 cup) may contain about 170,000 micrograms of polysorbate 80. Therefore, polysorbate 80 isn’t contained in vaccines at quantities that could possibly do harm.

Vaccines cause disease

In some areas of the world, some people have wondered whether vaccines could cause other diseases; for example, whether the polio vaccine was the source of AIDS virus. This theory gained significant attention in 1999 with the publication of a book by Edward Hooper, titled The River: A Journey Back to the Source of HIV and AIDS, which suggested that polio vaccine trials in Africa during the 1950s introduced the HIV virus into this population. However, subsequent testing found that this was not the case.

In 2003, internal political issues and distrust of westerners, and western medicine in general, led people in northern Nigeria to refuse the polio vaccine because they claimed that anti-fertility drugs and HIV viruses were present in the vaccine. The vaccines were tested in several laboratories and harmful substances were not found. Some Nigerians have also rejected the pertussis vaccine based on the belief that vaccines cause disease. In early 2018, rumors emerged suggesting that people dressed in army uniforms were forcing children to be immunized with vaccines containing monkeypox virus in order to kill people in the region.

Sources of misinformation

  • Science — Scientific studies must be designed properly and be reproducible. If a vaccine problem is suggested, studies must be completed to confirm that this is the case. Sometimes the new studies show that the original report was not correct. This is what happened in the U.K. in 1998 when a report by Andrew Wakefield suggested that the MMR vaccine caused autism. Several subsequent studies have shown this not to be the case; however, some people still believe that the first report was correct. This has led to decreased acceptance and use of the MMR vaccine and increases in outbreaks of measles and mumps in the U.K.
  • Anecdotal information — Personal stories are quite powerful; however, they do not always hold up when examined scientifically. Unfortunately, anecdotes are more emotionally compelling, easily passed from one person to another, and may lead others to make the wrong decision for their children. Stories in the media often contain anecdotes because they provide human interest; however, readers or viewers must determine whether the media source is trustworthy, whether the report provides a sensational or scientific background, and whether the purported ideas are plausible.
  • Websites — Unfortunately, there are many vaccine-related websites that do not provide accurate information about vaccines. Since the Web can be accessed around the world, misinformation can spread easily and quickly. Because many people turn to the Web to research health matters, some are misled into making poor health decisions when it comes to vaccines.

The World Health Organization's (WHO) Global Advisory Committee on Vaccine Safety provides information regarding how to judge websites. They also rate vaccine information websites throughout the world, so that people can trust the information they are finding.

Special considerations in the developing world

While the WHO recommends certain vaccines for most of the world’s population, not all countries are able to provide these vaccines. In the developing world, limited resources and accessibility play a significant role in which vaccines are offered. Unfortunately, it is because of these limits and worldwide travel that controlling disease can be difficult.

Each year about 19.5 million infants younger than 1 year of age remain unvaccinated throughout the world. (Source: World Health Organization (WHO) Global Immunization Data.)

Economic limitations not only limit which vaccines are provided, but also how many doses are administered and which types of a particular vaccine are provided. For example, even though lesser side effects occur from the acellular pertussis vaccine, many countries still use the whole cell version because it is less expensive, so more people can be immunized.

Newer, technologically advanced (and hence more expensive) vaccines may not be offered at all or for several years. One example is the HPV vaccine. Cervical cancer is the fourth most common cancer among women worldwide, and more than 85 percent of cervical cancer cases occur in the developing world. However, because of the price of the vaccine, uptake throughout the world has been slow. Work by advocates, donors, manufacturers and governments has been effective in establishing programs in some countries.

The Global Alliance for Vaccines and Immunization (GAVI) has been a leader in the efforts to provide vaccines to all at-risk populations, contributing more than $1 billion to support immunizations in the poorest countries. The programs may focus on a particular vaccine.

  • Polio eradication efforts have been underway since 1988. Partners including the WHO, Rotary International, U.S. Centers for Disease Control and Prevention (CDC), and UNICEF have provided programming, expertise and funding in an effort to rid the world of polio. To learn more about this campaign, visit the Global Polio Eradication Initiative website.
  • Measles initiatives have made considerable progress in decreasing disease and death caused by measles since its inception in 2001. Partners in this initiative include the American Red Cross, CDC, UNICEF, United Nations Foundation, and the WHO. To learn more about this campaign, visit the Measles Initiative website.

Reviewed by Paul A. Offit, MD on March 19, 2018

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.