Rotavirus And The Effectiveness Of Its Vaccines Biology Essay

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Most vaccines are not a hundred percent effective. They do prevent many types of diseases either bacterial or viral. Immunizations came out in different forms. They may be by injection, oral or intravenous. Some has been around for decades while others are just new in the market. Rotavirus vaccines are included in this genre. These were just newly introduced to the public in the year 2006 even though the disease has been discovered in 1973. In the earlier years, Rotashield® from Wyeth-Ayerst were released but then recalled. Today, there are two rotavirus vaccines available both administered orally. These are Rotateq®, manufactured by Merck & Co., Inc. and Rotarix®, made and distributed by GlaxoSmithKlein Biologicals. The question now is that, how effective are these vaccines against rotavirus that are said to prevent the virus mostly acquired by infants?

First, let us define this disease. According to the Centers for Disease Control and Prevention (CDC), rotavirus is the most common cause for severe diarrhea among children. Before the introduction of rotavirus vaccines in the United Sates in 2006, rotavirus resulted in the hospitalization of approximately 55,000 US children each year. There is an estimated 527,000 annual deaths worldwide.¹ In accordance to a journal contributed by Dr. Waisbourd-Zinman and his associates in an edition on August 2009 of American Journal of Infection Control, occurrences of rotavirus were through-out the year during their study. They based these on both in and out patient admissions in hospitals on a 4-year period from January 1, 2003 to December 31, 2006 in 3 Departments of Pediatrics of Schneider Children's Medical Center.² Dr. Bernstein, in his overview about rotavirus, mentioned that there was approximately about $1 billion expense on both direct and indirect cost for rotavirus disease per year.³ Usually, the signs of this illness include severe vomiting, diarrhea, high grade fever, some irritability and marks of dehydration.¹ Indications of this may involve paling and chapping of the lips, drying of the mouth, yellowing of the skin, drooping of the eyes, and/or unresponsiveness of the child. The feces of an affected person are most of the time watery, black and tarry, and sometimes there are visible spots of blood. It does smell worse than a usual stool. Symptoms that were earlier mentioned may not show all at once or all together. The longer the parents wait for more indications of the virus, the higher the risk for death of a child.

Going further on what this said rotavirus is, allow me to discuss the genetics of the virus. The CDC characterized rotavirus as having a wheel-like appearance once viewed under an electron microscope. They also mentioned that the name of this virus was derived from the Latin word rota which means "wheel".¹ The virus is from the family Reoviridae. As reviewed by Sanchez-Padilla and her associates, the virus is made up of three protein shells. These are the inner and outer capsid and a middle shell that secures an 11-segment, double-stranded RNA genome. The inner capsid (VP6), as they mentioned in the review allows the classification of the virus into different groups where in three groups (A-C) are identified as those of the human rotaviruses. According to studies, most frequently identified rotaviruses that infect human beings are from the A group. The two basic outer capsid proteins of this virus, VP7 (G glycoprotein) and VP4 (P protein) denotes the G and P serotypes of the virus. These are thought to be important in making the vaccines against the disease. These antigens permit the classification of rotaviruses into a dual nomenclature system, depending on the G-P antigen combination, mentioned in the review.4

Prevention is better than cure, which is why parents give consent to the child's primary care physician to vaccinate them. One of these vaccines was Rotashield®, a live attenuated vaccine. This was approved by the Food and Drug Administration (FDA) in August 1998, but then it was pulled back in October 1999 since it caused intussusception on children meaning a part of the intestine slipped back into an adjacent portion which causes obstruction.10 There was approximately 1 million doses used for 500,000 infants.9 Nothing was released from that said year until February 2006 that new oral vaccines were introduced to the public. Until the present day, pediatricians recommend this to the guardian or parent for infants to take starting from 6-10 weeks old up to 24 weeks old for Rotarix®11 and no older than 32 weeks for Rotateq®12. Rotarix® is administered as a 2-dose of 1 ml per dose oral series that fights against rotavirus disease caused by G1 and non-G1 types (G3, G4, and G9). There should be about 4-week interval between the first and second dose.11 Rotateq®, on the other hand is administered as a 3-dose with 2ml per dosage oral series that prevents rotavirus as well that is caused by G1, G2,G3 and G4 serotypes. There is a 4-10 week interval with each dose.12 With both vaccines, studies showed some adverse reactions which are sometimes normal once a foreign body is introduced to an infant and this is also the body's immune response. These may include fussiness or irritability, cough or runny nose, fever, loss of appetite, otitis media or well known as ear infection, nasopharyngitis or bronchospasm.11, 12 In the journals that were collected, including researches in Mexico, Europe, South Africa, Malawi and Philadelphia, all from different parts of the globe showed almost the same findings that investigates and analyzes effectiveness of these released vaccines.

In Mexico, Dr. Richardson and his colleagues acquired there data from January 2003 until May 2009 on Mexican children under 5 years old who died from diarrhea regardless of the cause. On that extent of time, they acquired information from the National Institute of Statistics, Geography, and Informatics and the Ministry of Health Information that collects all reports from the death certificates of the deceased 5 year olds. They did a comparison between the rate of deaths caused by diarrhea in 2008 and the data collected from 2003 through 2006. What they also took consideration of was the entire number of diarrhea-related deaths during the peak rotavirus-season which is on December up to May of 2008 and 2009 and the average number of deaths in the same months in baseline years. Rotavirus vaccines were introduced in 2006 and 2007; they considered 2007 as a transitional year and exempted this from their analysis. The result of their studies showed a proof of effectiveness of the vaccine for rotavirus in Mexican children. As Dr. Richardson and his associates wrote in their final journal, by December 2007, an estimated 74% of children who were 11 months of age or younger had received one dose of rotavirus vaccine. In 2008, there were 1118 diarrhea-related deaths among children younger than 5 years of age, a decline of 675 from the annual average of 1793 number of deaths within 2003 through 2006. From the usual yearly median of 18.1 deaths on every 100,000 children at baseline dropped to 11.8 in every 100,000 children in 2008. Between infants who were 11 months or younger, diarrhea-caused death declined from 61.5 deaths per 100,000 children at baseline to 36.0 in every 100,000 children in 2008. Using the baselines as their basis of comparison, diarrhea-related mortality was 29% lower for children who are between 12 to 23 months of age, with few of them being vaccine eligible because of their age. The death rate of children between 24 months to 59 months of age did not considerably decline. The cut in numbers of mortality caused by diarrhea showed constantly through two full rotavirus seasons (2008-2009). These physicians and other colleagues concluded that rotavirus vaccine did significantly well in reducing the death rate among Mexican children.5

On the other hand, about 70,000 infants were signed up for Rotavirus Efficacy and Safety Trial (REST) in Europe. Operated from 2001 through 2005, all were tested randomly, and with the use of placebo as their control drug. Timo Vesikari and his coworkers used this method to assess the effectiveness, capability, and safety of the vaccine Rotateq®. First oral dose of this vaccine or placebo were administered to infants who are at 6-12 weeks of age, following two more doses in a 4-10 week delay, until 32 weeks of age. The severity of episodes of Rotavirus gastroenteritis was determined through a 24-point severity scale which depends on the acuteness and period of fever, vomiting, diarrhea, and changes in behavior. According to the data they collected, a score of more than 16 was grouped as severe disease; 9-16 was moderate-to-severe; and 8 or less was considered mild. Parents and/or guardians of these infants who are enrolled for REST were told to record the child's temperature and the number of times the child had vomiting and diarrhea everyday for seven days after each administration of the vaccine, and at the same time the unfavorable events for 42 days after every dose. Their study and research showed data that Rotateq® is effective against rotavirus disease. They also mentioned in their journal that the vaccine reduced the severity of RVGE among infants in Europe.6

Dr. Madhi and his associates managed a randomized, placebo-controlled, multi-center trial in South Africa and Malawi. The total number of infants in the study was 4939, where in 64.1% were from South Africa, and the remaining 35.9% were from Malawi. The same as the studies conducted by Vesikari and his coworkers, Dr. Madhi and his associates' main purpose was to test the efficacy of a live oral vaccine that prevents Rotavirus gastroenteritis, but in this area, they used Rotarix® instead of Rotateq®. According to the journal, healthy infants of 5 to 10 weeks of age from South Africa were involved from October 2005 through January 2006 and from November 2006 through February 2007, before the predicted rotavirus seasons of 2006 and 2007. In Malawi, rotavirus was known to infect infants all year round, and so these children were enrolled from October 2006 through July 2007. The group assigned these infants randomly in a 1:1:1 ratio. Three groups were to receive two doses of the rotavirus vaccine during their 10 to 14 week of age; three doses of the vaccine at 6, 10, and 14 weeks of age; or three doses of placebo. Those infants that were at the two-dose vaccine group received a dosage of placebo on 6 weeks of age. Those vaccines that are usually given to infants routinely in accordance to the guidelines of the Expanded Program on Immunization (EPI) were jointly given with either the Rotarix® or the placebo. In this study, they gave the children's guardian or parent the choice of having their infant tested for HIV at the time when the first vaccine or placebo was administered or 1 month after the last dose. Whenever there are incidents of diarrhea or gastroenteritis between the dates the first dose of the vaccine or placebo was administered and the date when the child turned 1 year old, staffs would collect stool samples. With the use of enzyme-linked immunosorbent assay (ELISA) (Rotaclone, Meridian Bioscience), these samples were tested. All positive results for rotavirus from the testing were further analyzed using a reverse-transcriptase-polymerase-chain-reaction (PCR) assay, followed by a reverse hybridization assay to find out whether this is a G or P type. Some other testing such as blood sampling were collected and recorded as well as deaths that occurred on the time period. As a result of this study, they have recorded 70 out of 1443 infants in the placebo group (4.9%) and only 56 out of 2974 infants from the vaccine group (1.9%) had severe gastroenteritis caused by rotavirus.7 These are proof of efficacy of the rotavirus vaccine to children in South Africa and Malawi.

Effectiveness of newly introduced vaccines is always questioned. Even though there have been more than enough proofs that these rotavirus vaccines helped reduce the risk of infants having gastroenteritis, people especially medical doctors were still determined to get more people tested on the efficacy of this immunization. The same case as to how researchers from The Children's Hospital of Philadelphia analyzed the capabilities of Rotateq® and Rotarix®. They had done stool testing on infants who had acute gastroenteritis using ELISA from 1994 through 1995, where in the vaccine was not available yet. This made it possible for them to compare data from that period with the time where this immunization was already out in the public which was 2005 through 2006.8 Though the studies seemed to be limited since it was based on historical comparisons, these researchers found significant amount of data showing that from February 2006, when vaccines against rotavirus were introduced, a decrease of amount of infants who had cases of the disease showed outstandingly.

Transmission of rotavirus can come from vaccinated to unvaccinated infant. Young age, lack of pre-existing rotavirus antibodies, a large vaccine dose were correlated to the shedding of rotavirus vaccine.9 Fecal-oral contact is the main mode of transmission.1 This may be acquired from infrequent hand washing of parents or guardians of the infant or medical staffs in the hospital, where in this case it is already called a nosocomial rotavirus gastroenteritis (NRVGE). A 4-year prospective study was conducted in a pediatric clinic in Israel about this case. Within this year, there were a total of 356 children diagnosed with NRVGE without sudden happenings in the hospital and all were sporadic. 300 of these children showed NRVGE while staying in the hospital while 56 of them were readmitted due to acquiring this disease.2 Rotavirus itself is known to be stable in the environment. With that being a reason, consumption of contaminated liquids or foods and touching contaminated surfaces also causes transmission. As mentioned earlier, rotavirus is seasonal, too. If noticed, it occurs on winter months with annual epidemics from November through April of the next year. Most infected individuals are infants especially children who are less than 2 years of age.1 NRVGE rate showed age dependency, too. In the data collected, there were 1.8% (231/13,050) of all admissions of children under 12 months and 1.5% (89/6096) of all admissions of children age 1 to 2 years old, but there were only 0.3% (26/7879) of all admissions of children 2 to 5 years of age and only 0.1% (10/7692) of all admissions of children aging older than 5 years old. The same as the normal rotavirus disease, NRVGE cases are higher on winter months from October to January even though it occurs all throughout the year.2 Spread of the disease depends on where the person is. But according to Dr. Bernstein on her supplementary journal, there are no significant differences on occurrences of the disease between developed and developing countries.3

Those who had a healthy immune system, the virus that invaded the body only last for few days.1 Most of the time, hospitalizations caused by rotavirus gastroenteritis were mainly due to dehydration from severe diarrhea. Treatment for this one is usually just rehydration and intravenous fluids to be able to get back all electrolytes that were lost from the disease.1 Otherwise, to prevent for that complication to happen is much better than treating them. Clinical studies and research showed vaccine efficacy. Questions, concerns and criticisms are always there and no one could blame these people especially parents of these infants. Besides, rotavirus vaccines were just recently introduced.

AFTERWORD

In March 22, 2010, Food and Drug Administration (FDA) made a recall on Rotarix® vaccine. Healthcare practitioners were recommended to hold off on all administration of this in the United States since a study showed components of extraneous virus in the vaccine. PCV1 or porcine circovirus 1 DNA was found in Rotarix® manufactured by GlaxoSmithKline. There has not been any known safety risk or any disease of any type caused by PCV1 on human or animals. Also, it was identified that this type of DNA has already been present ever since the vaccines were introduced and Rotarix® has been widely studied and researched both before and after approval and it had a very good safety record. The analysts on this said PCV1 virus also studied the other rotavirus vaccine RotaTeq® and found no signs or strains from this. The report said that they will study the vaccine, PCV1 and risks or safety for this and will communicate with World Health Organization and other counterpart agencies in other countries.13

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