Each year about 2.1 million people around the world die from vaccine-preventable diseases. Most of the deaths are due to a lack of immunization. People may not receive needed vaccines because of availability, personal beliefs, vaccine safety concerns, or circumstances out of their control. Availability and circumstance are particularly important in the developing world:
Vaccines may not be readily available due to:
Individuals or groups may have beliefs that make them unwilling to get vaccines:
If you have heard of a vaccine safety concern and you do not see it discussed here, please contact us through e-mail at contactPACK@email.chop.edu.
Some people suffer an adverse event, or negative consequence, after receiving a vaccine. These events can be causal or coincidental.
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.
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, 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 do not even 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:
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:
The U.S. used OPV exclusively between 1963 and 1996. Once polio in this country was controlled, the recommendation was changed to use IPV.
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 is reactive in that 1 of every 5 people who get the vaccine experience tenderness, redness or swelling at the injection site and about 1 of 10 have headache, low-grade fever, pain, weakness, abdominal pain or diarrhea. 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 of every 50,000 - 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 for 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.
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 mental retardation; 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.
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.
Sometimes needles and syringes have been reused or not discarded properly. In these instances, blood-borne diseases, such as hepatitis 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.
Vaccines must be kept at certain temperatures and used by certain expiry dates. This is much easier 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 is needed and staff members should be taught to rotate stock to help avoid these 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-olds because of contamination with another type of bacteria. Fortunately, no one was reported to have suffered adverse events from this error.
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. None of the studies designed to determine causality have found vaccines to be a cause of these diseases.
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, there is no reason to believe that the polysorbate 80 will cause infertility, particularly in the quantities used in vaccines.
In some areas of the world, there has been speculation that vaccines cause diseases distinct from those they are preventing. For example, there has been concern that 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 to this population. However, subsequent testing found that this was not the case.
More recently, internal political issues and distrust of westerners, and 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.
While the WHO recommends certain vaccines for most of the world’s population (tuberculosis, polio, diphtheria, tetanus, pertussis, hepatitis B and measles), 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 22 million infants less 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, which prevents cervical cancer, and costs about $125US per dose (3 doses needed). Not only is cervical cancer the second most common cancer among women worldwide, 80 percent of the deaths resulting from cervical cancer occur in the developing world. Work by advocates, donors, manufacturers and governments will be required to establish programs in countries where this vaccine could have the most profound effects.
In order to provide vaccine in some resource-limited areas of the world, several programs operate to provide vaccines to all at-risk populations. The Global Alliance for Vaccines and Immunization (GAVI ) has been a leader in these efforts, contributing more than $1 billion to support immunizations in the poorest countries. The programs may focus on a particular vaccine.
Updated: January 2013
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