Poliomyelitis

Acute poliomyelitis is a viral infection primarily affecting infants and young children. The virus is transmitted primarily person-to-person via fecal-oral route, although pharyngeal spread via throat secretions is more likely in environments with good sanitation. The infection occurs in the gastrointestinal tract and then spreads to regional nodes in the body, and in rare instances to the nervous system.

 

About 95% of infections are asymptomatic or limited to a non-specific fever. Between 4-8% of infections results in minor symptoms that are similar to any viral illness: sore throat and fever, malaise, headache, nausea, and vomiting. The classic clinical sign of severe cases is the acute onset of asymmetric flaccid paralysis with fever at onset. Severe symptoms, accounting for about 1% of cases, may also include muscle weakness, severe muscle pain, and stiffness of neck and back. The site of paralysis depends on the location of nerve cell destruction. Paralysis of respiratory or swallowing muscles is life threatening. Paralysis present after 60 days of infection is likely permanent. Further muscle weakness may occur many years after the original infection (“Post-polio syndrome”). However, this is infrequent and not related to a persistence of the virus itself. About 2-5% of children and 15-30% of adults with paralytic polio will die.

Humans are the primary reservoir, occurring mainly in individuals with asymptomatic infections, especially children. Long-term carriers have not been found. "Wild polio" is the term used to describe the virus in the environment.

 

Prevalence  & Incidence

United States

Prior to the 1950s, there were 13,000-20,000 cases of paralytic polio cases and more than 1,000 polio-related deaths annually in the United States. An outbreak of polio in 1952 and 1953 increased the number of cases to 58,000 and 35,000 respectively. In 1960, the number of paralytic cases reported dropped to about 2,500, with a further drop to 61 cases in 1965. The last case of paralytic wild polio in the United States was reported in 1979. The United States was considered polio-free in 1985, after the last case involving an immigrant who received an oral-live vaccine spread the disease to a few un-vaccinated children in an Amish community. The last confirmed case of wild polio in the Western Hemisphere occurred in Peru in 1991. The established Public Health and Medical Communities attribute the eradication to the widespread innoculations with the polio vaccine starting in 1955.

 

World

In 1998 the world-wide incidence of polio was 350,000 cases. This same year, the World Health Organization and UNICEF initiated a global effort to eradicate polio. To date, the disease has been eradicated in the Americas, Europe, and 36 Western Pacific countries including China and Australia. A few areas of the world continue to report cases. In 2001 480 cases were reported in 10 countries and in 2006 there were just over 1,900 cases in 16 countries. Currently, polio exists in only a few countries in Asia and Africa (Afghanistan, India, Pakistan, and mainly Nigeria). Some of this is related to lack of health infrastructure due to war while concerns over vaccine safety have decreased immunization rates. Because polio has not been globally eradicated, importation of the virus remains a risk for non-endemic countries like the U.S..

 

Resistance and Susceptibility

Polio can be caught only once in a lifetime. Immunity is life-long and occurs in both clinically symptomatic and asymptomatic cases. Susceptibility to infection is common. However, paralysis is rare. The rate of paralysis among infected non-immune adults is higher than in non-immunized infants and young children. An increased rate of paralysis is found among pregnant women. Polio during pregnancy is associated with increased risk of abortion, premature birth, and stillbirth.

     

The Vaccine and Vaccination

Two types of vaccine have been developed for this disease: 1)  the oral-live attenuated type and  2)  the injected inactivated type. Although the oral-live type was primarily used between 1950-1999, it is no longer given in the United States. In 1996, the CDC recommended a transition policy to increase use of the injected-inactivated vaccine and decrease the oral-live vaccine. In 2000, they recommended the exclusive use of the injected-inactivated type. Currently, the only polio vaccine offered in the United States is called Ipol (produced by Sanofi Pasteur). It contains the whole virus in an inactivated form thus eliminating the potential of infecting people or causing a paralytic reaction.

 

The current recommended polio vaccine schedule from the Centers for Disease Control and Prevention (CDC) is as follows:

One dose at each of the following ages: 2 mos, 4 mos, 18 mos, 5 yrs

The third dose can be given anytime between 6–18 months

The fourth dose can be given anytime between 4-6 years of age

 

The CDC does not recommended routine vaccination for persons over 18 years old who live in United States. Although it is recommended that adults in the following high risk groups consider vaccination:

Un-vaccinated individuals traveling to polio-endemic areas of world

Individuals working in laboratory and handling specimens that might contain polio viruses

Healthcare workers or individuals who have close contact with a person who could be infected with the virus

 

Ingredients of the injected-inactivated vaccine

3 inactivated virus strains

M-199 culture medium (saline, vitamins, amino acids, sucrose, glutamate, human albumin).

2-phenoxyethanol – 0.5 % of vaccine solution

Formaldehyde – 0.02% of vaccine solution

Residual amounts of 3 antibiotics

Traces of calf serum – 1 part per million (left over in vaccine solution)

 

Side Effects

Several sources report that standard side effects associated with other vaccines are not common with polio vaccine. According to Robert W. Sears, standard side effects include pain, redness, and swelling at injection site, fever, crying, vomiting, diarrhea, poor appetite, sleepiness, headaches, body aches, small nodule at injection site lasting for several weeks, and a rash over the whole body or limited to one area.

 

Although rare, the injected polio vaccine may cause a severe allergic reaction. Therefore it is recommended that it not be administered to persons who have experienced a severe allergic reaction after a previous injection or those who have reactions to streptomycin, polymyxin B, and neomycin. The only unusual reactions reported is Guillain-Barre syndrome, which has also been reported after various other vaccines. This is extremely rare (although the number of cases is unknown). It is believed that the risk of the injection causing serious harm, or death, is extremely small.

 

Arguments Against the Vaccine

Iatrogenic cases

One major concern is related to the use of the oral polio vaccine (OPV). It has the ability to revert to a form that can develop neurological infection and cause paralysis. Disease caused by the vaccine is indistinguishable from the wild type. It is reported that 8 children a year in the United States were paralyzed by the OPV vaccine when its use was widespread. Although this incidence is considered rare compared to the thousands of children who were successfully inoculated, it still represents irreversible damage to the lives of these individuals and their families.

While the use of OPV in the U.S. and the United Kingdom has been halted and replaced by the injected-inactivated type, it continues to be used around the globe. The World Health Organization argues that OPV’s use is justified in high endemic areas because the benefits of immunizing large populations quickly and efficiently outweigh the direct risks of iatrogenic polio cases. I would argue that this is a risk not worth taking because it puts the world’s most vulnerable children at higher risk. Immunodeficient children are 7,000 times more at risk of developing iatrogenic polio than healthy children. Given that the endemic areas in the world are in third world (and often war-torn) countries, these children are born into a world where their health is compromised from the outset. Many have a reduced ability to fight off even a small quantity of subclinical virus. OPV should be switched to the injected type worldwide - no exceptions.

 

Vaccine ingredients

The most controversial aspect of the vaccine is the concern about the safety of using human or animal tissues and blood products to make the vaccine. Specifically, in this case, concern is related to the use of infected rhesus monkey kidney cells used in preparing the vaccines in the late 1950s. The cells were infected with the Simian Virus-40 (SV-40) which was later found to cause tumors in rodents as well as linked more recently with some forms of cancer in humans (e.g. non-Hodgkin’s lymphoma, brain and bone tumors, and mesotheliomas). This SV-40 was present in stocks of the injected polio vaccine (IPV) that were used from 1955-1963. It is estimated that 10-30 million Americans may have received a dose of that was contaminated. Moreover, it is believed that vaccines manufactured in the former Soviet Union up to 1980 (and distributed throughout USSR, China, Japan, and a few African countries) may have also been contaminated. Together these estimates suggest the possibility that millions of people were exposed to SV-40.  Although several large studies did not find an increased incidence of cancer in individuals who may have received the vaccine, the question remains highly controversial. Other concerns that the vaccine causes sterility have grown in recent years in Nigeria and a few other African nations. As a result disease incidence has increased due to a decrease in inoculations. 

 

Still others have concerns over the inclusion of glutamate (MSG) and formaldehyde in the vaccine. MSG has been the subject of heated debates for many years. Some studies show MSG to be a excitotoxin which causes damage to brain function. Arguments against formaldehyde exist because it is considered a carcinogen by OSHA and the EPA. It has been shown to cause kidney and genetic damage. Despite these chemicals being present in only trace amounts, some people still object to their presence in general.

 

Practical reasons

Many parents do not want to vaccinate their child from polio because the disease no longer exist in the U.S.  These parent are ok with skipping the vaccine because the chance of un-vaccinated child catching polio while living in US is nearly zero. And, because the prevalence is nearly zero across half the planet, the risk they are putting their children in by not being vaccinated are minimal.  Still other parents are concerned over adding the vaccine in with other vaccinations during early infant years. Some of these parents may consider vaccinating kids as they get older.

 

Varicella

Chickenpox (varicella) is an acute, generalized viral disease characterized by a sudden onset of slight fever, mild constitutional symptoms and skin eruptions. The skin eruptions transition from maculopapular in the first few hours to vesicular for 3-4 days, followed by a granular scab. Skin lesions occur in successive groupings with several stages of maturity present simultaneously. They tend to be more abundant on covered areas of the body than exposed parts. They may appear on the scalp, in the axilla, and on mucous membranes of the mouth, upper respiratory tract, and conjunctivae. They also tend to occur in areas of irritation such as sunburn or diaper rash. Some may be overlooked, escaping observation. Infections can be asymptomatic, mild, or atypical. Severe fever and constitutional symptoms may occur, especially in adults.

 

The disease is caused by the human alpha herpesvirus 3 (varicella-zoster virus). Humans are the only reservoir. Transmission is person-to-person by direct or indirect contact. Direct contact is from droplets or the airborne spread of vesicle fluid or secretions from the respiratory tract of persons with chickenpox or from vesicle secretion from persons with herpes zoster. Indirect transmission can occur via freshly soiled discharge from vesicles and mucous membranes of infected persons. Chickenpox is one of the most highly communicable diseases. It is most infectious in the early stages of eruptions. Herpes zoster, however, has a lower transmission rate. The incubation period is 2-3 weeks. The incubation period may be prolonged in immuno-deficient individuals and those with passive immunity. The disease is communicable 1-5 days before the onset of the rash, but not more than 5 days after the appearance the first vesicles appear. Susceptible individuals should be considered infectious for 10-21 days after exposure.

 

After infection the varicella virus remains latent in the body, which may reactivate years later as herpes zoster (shingles). Herpes zoster occurs more often in adults than children. It manifests as a latent varicella infection in the dorsal root ganglia. It is characterized by vesicles with a red base occurring in patterns associated with sensory nerves of a single or group of dorsal root ganglia. Lesions appear in groupings in an irregular pattern on the nerve pathway and are usually unilateral. Common symptoms include severe pain and parethesia.

 

Resistance and Susceptibility

Susceptibility is universal among individuals not previously infected. Infection confers long immunity, with second attacks being rare ( it does not confer lifelong immunity as is commonly misunderstood). It is not considered a serious disease due to its typically mild nature, especially in children. Adolescents and adults who contract the disease often feel more sick than children. Complications of the disease are extremely rare (<1% of cases) and include symptoms such as skin infections, pneumonia, arthritis, bleeding problems, kidney or liver problem, and neurological symptoms.

The disease is most serious for adolescents or adults with compromised immune systems. Groups at increased risk for severe or fatal infections are neonates whose mothers are not immune or individuals with leukemia. Infection during the first half of pregnancy can result in congenital malformations. Moreover, newborns born to mothers who contract the disease 5 days before or up to 2 days after delivery are at high risk of a more aggressive case of the disease and higher mortality rate. Populations at higher risks for developing herpes zoster include: adults with cancer, immuno-deficient individuals, and persons on immunosuppressive therapy.

 

Prevalence  & Incidence

Chickenpox is not as common as it used to be. Prior to widespread vaccination in the mid 1990s, 3.5 to 4 million cases were reported annually. Some estimates indicated a 75% decrease in incidence in the last 10 years, with approximately 50,000 cases reported a year. However, since the disease does not require reporting to the CDC, accurate annual incidence rates are hard to ascertain.

 

Before vaccination was common, chickenpox accounted for about 50 deaths a year in the United States. Now deaths are very rare, occurring in 1 out of every 65,000 cases. Although children account for most cases, the majority of deaths occur in adults. Deaths associated with the disease in adults are primary due to viral pneumonia.  Septic complications and encephalitis cause death in children. In fact, reports state that mortality rate due primary to varicella has declined significantly in countries around the world.

 

The incidence of shingles and post-herpetic neuralgia increase with age. Groups at higher risk for developing the disease include those immunosuppressed, persons with HIV infection, and persons with diagnosed malignancies. Intrauterine infections and varicella before 2 years of age are associated with developing shingles at an early age.

 

The Vaccine

Widespread vaccination with the live virus began in the mid 1990s, with over 40 million doses administered. The recommended inoculation schedule for children is at 12 months and 5 years of age. The vaccine is not give prior to 1 year of age because live viruses such as this do not work well before this age. Currently, the United States and Canada are the only countries to routinely administer the vaccine.

 

The vaccine is not designed to confer lifelong immunity, but to protect against the disease. Studies indicate that children lose their protective immunity in 5-10 years. Therefore a second booster shot is given to provide longer lasting protection. However, it is not know how long the second dose lasts. Moreover, the vaccine does not provide perfect protection. Individuals who get the vaccine may still catch the virus later, but it will be a much milder form.

 

Vaccine ingredients

Live virus

Sucrose

Saline solution

Gelatin

MSG

Potassium (as an electrolyte)

Residual components of the Merck human diploid cells (e.g. DNA and cell proteins)

EDTA (a chemical used in a variety of products) – trace amounts

Neomycin (antibiotic to keep cell culture sterile) – trace amounts

Trace quantities of cow fetus serum

 

Side Effects

The vaccine is believed to be safe. Standard side effects (see polio side effects above) occur at the same rate as with other vaccines. However, this vaccine has some additional unique reactions. Approximately 4-5% of vaccinated children develop a rash 2 weeks after the shot. In other instances, flu-like symptoms may occur (e.g. body aches and pains).

 

Other reactions reported since the vaccine came on the market include: bleeding problems, pneumonia, skin infections, severe life-threatening rash, and nervous system effects such as Guillain-Barre syndrome, encephalitis, seizures and stroke. The reactions are also complications of the disease itself so both disease and vaccine are associated with risks. As of May 2006, no deaths have been attributed to the vaccine. A few cases of vaccine-related chickenpox have been reported in children with weak immune systems.

 

Arguments against the varicella vaccine 

Practical reasons

One of the main reasons some parents choose not to vaccinate their children is that they do not view the disease as particularly threatening. They understand that it is bothersome, but it is usually harmless in the long run. Many parents view this as a normal rite of passage during childhood. In fact, some parents want their children to catch the disease because having the disease confers greater immunity than the vaccine itself. This is especially important for girls as immunity during adult child bearing years is important. Still other parents worry that the shot will wear off causing their child to become susceptible when an adult.

 

Interestingly, the primary reason some parents vaccinate their children is because they really don’t want their child to have chickenpox. They want to avoid the difficult week home with sick children or teens and avoid potential complications (albeit they are rare). It is also argued that the vaccine makes for a milder course of the disease if a child later gets it. I consider these all luxury excuses of our modern world. People don’t want to be bothered by “annoying” life events. Given that wild-exposure confers a longer immunity than the vaccine and it’s boosters, it only seems obvious not to vaccinate normal healthy children.

 

Vaccine ingredients

Still other parents chose not the vaccinate their children because they object to either the manufacturing process or ingredients in the vaccine. MSG continues to be a controversial additive. Some people are severely allergic to it and still some research shows it negatively affects brain function. While the amount of MSG in the vaccine is drastically smaller than the amount of MSG found in a typical restaurant dinner, objections to it being present at all still exist.

Controversy exists from the use of cow fetus serum. Concern exists regarding the safety of using animal tissues so to avoid other infectious diseases associated with prions (e.g. Mad cow disease). To date, there are no screening methods for prions.

 

Summary

Given the relatively mild disease course and low mortality rates associated with chickenpox, we can conclude that this is not a serious disease. For the majority of the population, the varicella vaccine appears to delay possible contraction of the disease or set a person up for reduced immunity later in life. These risks do not outweigh the benefits of the vaccine. However, choosing to vaccinate children that are immuno-compromised require special thought and consideration. It may be in there best interest to be vaccinated given the potential severity and risks associated with contracting the wild type of chickenpox.

 

Although the vaccine may make sense for a small portion of the population, it doesn’t make sense for the larger population of children. It’s worth wondering whether the widespread administration is less about protecting public health as potentially more due to pharmaceutical companies wanting to cover the costs of researching and producing the vaccine.

 

Resources

Control of Communicable Diseases Manual. Abram S. Benenson (Ed). 16th Edition, 1995. Report of the American Public Health Association.

Polio Vaccine. Wikipedia, http://en.wikipedia.org/wiki/Polio_vaccine

How to Raise a Heathy Child…in Spite of Your Doctor. Robert S. Mendelsohn. Ballantine Books. New York. 1984.

Varicella vaccine. Wikipedia, http://en.wikipedia.org/wiki/Varicella_vaccine 

The Vaccine Book: Making the Right Decision for your Child. Robert W. Sears. 2007. pp. 268