A Cost-Benefit Analysis of Vaccines

Worries about safe manufacture, the effects of additives, and the side effects of vaccines have been subjects of public concern in recent years, but the benefits far outweigh potential costs.

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Vaccines have helped transform health and health care around the globe. It's hard to believe that diseases like polio, smallpox, diphtheria, and whooping cough were common ailments within the last century. Today, these diseases are virtually or totally eradicated. This change is largely due the development of vaccines, which give our bodies the tools to fight disease-causing viruses and bacteria more effectively than they can by themselves.

The CDC has calculated that many millions of additional deaths would be expected each year if we were to stop vaccinating today. The GAVI alliance, a non-profit that works to bring vaccinations to people across the globe, estimates that even today, every 20 seconds one life is lost to vaccine-preventable diseases: this is the equivalent of 1.7 million preventable deaths worldwide each year. Other estimates suggest that this number is much higher, at three million.

Despite their well-documented benefits, vaccines are frequently the subjects of public concern. Worries about safe manufacture, the effects of additives, and vaccines' side effects are some of the concerns that have accompanied vaccines in recent years.

It is possible to weigh the costs or risks of vaccines against the benefits they make possible and come up with a cost-benefit ratio. Considering what vaccines are all about, including how and where they are made and which concerns are legitimate and which appear unfounded yields a cost-benefit calculation that isn't as tricky as you might believe.

WHAT IS A VACCINE?

Vaccines help the body fight disease by giving it a "preview" of a pathogen that it might someday have to fight in earnest. Vaccines contain a version of a microbe, often an inactive form of a virus or bacterium, which triggers the immune system to make antibodies. Live, "attenuated" organisms in vaccines like measles-mumps-rubella (MMR) are weakened forms of the microbe -- they trigger an immune reaction, but they are not as virulent as the real thing, so they are less able to cause infection. Still, the immune system treats the live viruses in vaccines as if they were "real," and quickly creates antibodies against them.

Other vaccines, like hepatitis A and influenza, use "killed" organisms, which are also effective in triggering the immune system to make antibodies, yet they pose even less risk of infection because they are less intact. The immune system clears the microbes, or pieces of microbes, from the body, but, as with a regular infection, the antibodies remain. In this way, if an actual microbe is encountered, the body will be well prepared to attack it -- because it already has antibodies against it -- before the microbe leads to a full-blown infection.

RISKS AND ADVERSE REACTIONS

It's natural to be nervous about things we put into our bodies and those of our children -- particularly those that are injected into us -- so some people are concerned about the safety of vaccines. From what we know, there are some concerns that are warranted and some that are not, based on the evidence.

Additives Appear Safe

There are a number of components to vaccines. Besides the pathogen in the vaccine, there are other ingredients, some of which have raised questions or concerns in the past. The main ingredients in vaccines include suspending fluid, preservatives, stabilizers, and adjuvants, which enhance the response of the immune system to the particular antigen in the vaccine.

Vaccines may also contain antibiotics to stop the growth of bacteria in the suspension; egg protein (in flu and yellow fever vaccine), which comes from the manufacturing process; formaldehyde, which is used to inactivate bacteria; monosodium glutamate (MSG) as stabilizer against light, heat, humidity, and acidity; and thimerosal, which is a preservative containing mercury.

People have worried about thimerosal being linked to developmental problems, though most childhood vaccines no longer contain it. It is removed toward the end of the manufacturing process, although tiny amounts may still remain in the final product. Flu vaccine is one type containing small amounts of mercury. The American Academy of Pediatrics suggests that the mercury in vaccines is so negligible that there is no possibility for it to effect early development. They also point out that since mercury has been removed from vaccines in recent years, autism rates have actually increased, suggesting that there is absolutely no link between mercury and autism, as some have been concerned about.

Another additive, formaldehyde, is found in such tiny amounts that there is virtually no risk of it posing harm to the vaccine recipient. Likewise, the antibiotics used in the production of vaccines show up in tiny or undetectable amounts in the final product, so the safety concern is almost nil. Aluminum salts or gels are common adjuvants: While aluminum can pose problems in high doses, the amount in vaccines is thought to be quite safe.

These additional ingredients in vaccines can sound a little mysterious, but the bottom line is that they are found in such tiny amounts -- or removed by the end of the manufacturing process -- that the risks are vastly overshadowed by the many benefits that come along with vaccination.

Reactions May Occur

A more realistic concern is that giving a vaccine may spark an immune reaction that is similar to -- although typically much milder than -- the disease the vaccine is designed to protect against. Symptoms can mirror those caused by the pathogen itself: in the case of the flu vaccine, for example, common side effects may include fever, aches, and cough. These effects are usually quite tolerable, and go away within a few days.

Some people cannot tolerate certain vaccines, like the influenza vaccine, because chicken eggs are used to grow the vaccine in the lab (yellow fever is another that uses eggs). The residual egg protein in the vaccine can pose a problem for people who are egg-allergic. The measles-mumps-rubella (MMR) vaccine typically contains a much smaller amount of egg protein, and does not usually cause a reaction in egg-sensitive people. Gelatin is another additive that can cause an allergic reaction, though it is also very rare.

Major Adverse Events Are Real but Rare

Beyond the considerations mentioned above, there are some adverse events that are clearly the result of vaccines, though they are extremely rare. Some people may experience a severe allergic reaction to the vaccine, which can be serious. Symptoms can include fever, swelling of the throat, difficulty breathing, dizziness, hives, fast heartbeat, and seizure.

The FDA and CDC closely monitor and catalog these adverse events, through the Vaccine Adverse Events Reporting System (VAERS), which is designed to detect new adverse events, track increases in events, identify risk factors, determine the safety of new vaccines, and identify lot numbers that are linked to more adverse events. VAERS has its limitations. It is difficult to determine whether the adverse events reported actually have to do with the vaccine or another, unidentified variable. Studies have found that the VAERS data contain "strong biases," and that the specific risk associated with vaccines is virtually impossible to calculate based on the data. Researchers have more recently turned to other means, like large-linked databases (LLDB), from which they can draw from patients' complete medical histories in addition to their vaccine history, which can provide a more complete picture.

Roughly 30,000 adverse events in the United States are reported to the organization each year, a miniscule number given the number of vaccines administered in year. Of these reported events, only 10 to 15 percent are determined to be serious, resulting in hospitalization, serious health problems, or death.

Looking at the total number of vaccines given over a ten-year period -- 1.9 billion -- there were 128,717 reports of adverse events in total, which includes both serious and non-serious events like side effects including fever, rash, and soreness at the injection site. This comes out to only about 0.006 percent of the people who are vaccinated experiencing an adverse effect -- a tiny number, indeed.

Despite the possible shortcomings of the standard VAERS method of reporting, it is probably safe to say that adverse events are extraordinarily rare, and that the risks of not vaccinating strongly outweigh the risks of getting vaccinated.

Presented by

Alice G. Walton, PhD, is a health journalist and an editor at The Doctor Will See You Now.

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