group synthesis

Group Synthesis on the Effectiveness of the Influenza Vaccination

Lindsey Bates, Elizabeth Kendig, & Christie McCormick

Nursing Science: Research

NUR 3223

Dr. Patrick Heyman

Palm Beach Atlantic University

April 20, 2008

The Effectiveness of the Influenza Vaccination

Influenza causes an estimated 10,000 to 40,000 deaths annually in the United States (Nichol, Margolis, Wuorenma, & Von Sternberg, 1994). According to the World Health Organization (2008), “influenza is a viral infection that affects mainly the nose, throat, bronchi and, occasionally, lungs. Infection usually lasts for about a week, and is characterized by sudden onset of high fever, aching muscles, headache and severe malaise, non-productive cough, sore throat and rhinitis.” According to the CDC, the current recommendation for the influenza vaccination are people at high risk including infants, pregnant women, people with chronic health conditions like asthma, diabetes or heart disease, and people 65 and older. Eighty percent of deaths due to influenza occur in elderly adults 65 years and older (Nichol et al, 1994). But influenza does cause substantial morbidity and mortality in all age groups. Influenza also causes restriction of activities due to symptoms, and it accounts for millions of days lost from work each year (Drake et al, 1995). Influenza is something that needs to be considered in all age groups and preventative measures should be taken. Listed below are 9 articles that we reviewed to study the relationship the influenza vaccination has on influenza. Shown in table 1 on pages 8 – 10 are each of the article’s title authors, study type, population of interest, and conclusion.

Review of Literature

Mangtani, Cumberland, Hodgson, Roberts, Cutts, & Hall (2004) studied the relationship of the influenza vaccine against hospitalization and death in individuals over the age of 64. The researchers gathered data from the General Practice Research Database (GPRD) from 1989-1999 in Wales. The data consisted of all prescriptions, vaccinations, deaths, and data on severe illness requiring referral to the hospital. The study linked influenza vaccination to subsequent hospitalization and death of the individuals. The study showed the rates of hospitalization for acute respiratory disease were on average, reduced during the influenza season to 21% (95% CI, 17%-25%), and the risk of death due to respiratory disease in the influenza season went from 1.32 to 0.88, providing a summary vaccine effectiveness of 12% (95% CI, 8%-16%). Overall, this study was good for a retrospective historical cohort. A possible weakness was that the GPRDs used their own judgment to determine if the deaths were related to influenza or not based only on the medical records.

Drake, Hauge, Lind, Magnan, Margolis, McFadden, Murdoch, et al. (1995) studied the relationship of the vaccination against influenza in healthy, working adults ages 18-64 and from the Minnesota St. Paul area. The study consisted of a randomized, double-blind, placebo-controlled trial. The subjects were recruited through advertisements at work sites, local newspapers, and recruitment sessions at shopping malls. The subjects received either the influenza vaccine or placebo according to a computer-generated randomization schedule. The results of this study showed, those who received the vaccine reported 25 percent fewer episodes of upper respiratory illness than those who received the placebo (105 vs. 140 episodes per 100 subjects, P<0.001), 43 percent fewer days of sick leave from work due to upper respiratory illness (70 vs. 122 days per 100 subjects, P = 0.001), and 44 percent fewer visits to physicians’ offices for upper respiratory illnesses (31 vs. 55 visits per 100 subjects, P = 0.004). The cost savings were estimated to be $46.85 per person vaccinated. This was a strong study in that it was an adequate sample size, the study year was characterized by an excellent match between the vaccination strains and circulating strains, and there was a thoroughness of evaluation of effects. Some weak points to this study were there was regional bias, the follow-up period relied on the subject’s interpretation on the data, and the study did not mention exactly how they randomized the study factors.

Bodkin & Klopper (2003) studied the relationship of naturopathic influenza prevention and influenza vaccination against influenza infection in healthy individuals ages 8-50. The method used for this study was an open-label, two group, parallel study. It consisted of a self-report questionnaire. Advertisement was used at a clinic in Johannesburg to promote the research study. The target population consisted of 10761 individuals and by use of non-probability sampling extracted a sample of 88. The naturopathic influenza prevention methods did not reduce the risk of contracting influenza infection but they did reduce the duration of febrile illness as compared with trivalent influenza vaccination. The naturopathic group was less likely to visit a medical practitioner, clinic sister or pharmacist in order to resolve the influenza. However, they are as likely as the vaccinated group to commence new treatment plan. Neither method of influenza prevention resulted in a significant reduction in absenteeism from work. The trivalent vaccinated group had significantly more side-effects than the naturopathic group. This study was weak because it did not discuss the power, and there was not enough evidence to accept or reject the null hypothesis so it should have mentioned the power.

Crocetti, Arniana, Bordoni, Maciocco, Zappa, & Buiatti (2001) studied the effectiveness of influenza vaccine in reducing hospitalization among elderly subjects in a community in central Italy. The researchers studied elderly residents age 65 and older in the Health District no.10 in the Tuscany region. The design of the study was a case control study in which for each case (275), two controls (550) were randomly chosen among subjects alive at December 1, 1994 and matched sex, age(+/- 5 years) and municipality of residence. To gather information the researchers used a survey, both by mail and telephone. The research showed the influenza vaccine to be successful in reducing 33% of hospital admissions due to pneumonia and influenza in given conditions. This study has some weaknesses in that there was geographical bias and bias relating to the recall period, and there was also no way for the researchers to check their information with physicians records due to the lack of files.

Mayo & Cobler (2004) studied the relationship between patient perceived barriers and motivators and decision-making conflict between two groups of hospitalized patients in regards to the influenza vaccination. The investigators used a survey which was designed to capture vaccination barriers and motivators, and a decisional conflict scale which measured uncertainty about the course of action to take. Methods of data collection for this study compromised mailed surveys and organizational databases. The findings showed that the top motivator for vaccinated patients was having the vaccine in the past (p=.000). In patient decisional conflict, patients that were non-vaccinated scored highest in certainty and feeling informed, and patients in the vaccinated scored highest in the certainty and feeling supported. Vaccinated patients were older, classified themselves as higher risk, had more education, and rated a lower health status. Only 76.9% of high risk hospitalized patients were having been reported receiving the vaccine. Barriers included the fear of side effects and contracting the flu from the vaccines related to knowledge deficit. Patient decision making conflict overall stated that the non-vaccinated were less certain about the vaccination than the vaccinated. Some weaknesses to this study were that the overall sample size was not adequate, and the associations between variables was also not adequate.

Nichol, Nordin, Nelson, Mullooly, & Hak (2007) studied the effectiveness of the influenza vaccine in the community-dwelling elderly. The investigators analyzed data among 18 cohorts of HMO’s during ten influenza seasons. The purpose was to provide a long term view of effectiveness while addressing potential bias and residual confounding. The total amount of persons studied was 713, 872. Baseline characteristics of vaccinated versus non vaccinated were compared, as well as subgroup analyses to explore for heterogeneity in levels of vaccine effectiveness and to divide the study population into more homogenous strata that might reduce the effect of residual confounding bias. During the ten seasons, there were 4,599 hospitalizations for pneumonia and influenza and 8,796 deaths. Increasing age and the presence of one or more high-risk medical conditions at baseline were the strongest predictors of hospitalization or death. Vaccination was associated with reductions in hospitalization for influenza and pneumonia (27%, adjusted OR 0, 73; 95% CI 0.68-0.77), and death (48%, OR 0.52; CI 95% 0.50-0.55). There was interaction between vaccination and high-risk status for hospitalization (p=0.004), between vaccination and sex (p=0.03), and outpatient visits (p=0.03). A weakness of this study was it did not evaluate frail elderly persons such as those living in nursing homes or institutionalized due to impaired immune responses. The researchers also stated that the residual confounding may have influenced lower results but would still be significant. Misclassification of vaccination status could have also been a factor in which there was a failure of a record receipt of the vaccine.

Nichol, Mendelman, Mallon, Jackson, Gorse, Belshe, Glezen, et al (1999) studied the safety and effectiveness of the intranasally administered live, attenuated influenza virus (LAIV) vaccine for reducing illness in healthy working adults. The researchers conducted a four month randomized, double blind placebo trial on 4,561 participants who were 18-25 years old. Results showed that the vaccine did not reduce the proportions of people who experienced at least one febrile illness. However, it did significantly reduce the number of severe febrile and upper respiratory tract illness’ that occurred. The vaccine was also was able to reduce the number of days people missed from work, trips to healthcare providers, and prescriptions filled. Overall, this study was good. It was shown that the LAIV vaccine reduced illness, absenteeism and healthcare use amongst working adults. Limitations were not discussed in the study; however, a weakness to this study was that their research depended on the subjects self-reported illnesses which are not as reliable as a physician’s diagnosis. They also only included data for subjects they were able to reach for a follow up which could have enabled them to capture important outcome information.

Nichol, Margolis, Wuorenma, & Von Sternberg (1994) studied the relationship between the flu vaccine and its efficacy and cost effectiveness in elderly patients living in the community. The researchers used administrative data bases to study men and women over 65 years of age who were enrolled in a large health maintenance organization. They examined the rate of vaccination and the occurrence of influenza and its complications in each of the three influenza seasons from 1990-1993. In conclusion, for elderly citizens living in the community, vaccination against influenza is associated with reductions in the rate of hospitalization and in deaths from influenza and its complications, as compared with the rates in unvaccinated elderly persons, and vaccination produces direct dollar savings. Overall this study was well done. It did have regional bias but some positives were its large sample size and its long duration.

Canning, Phillips, & Allsub (2004) studied to identify the beliefs that influence and discourage influenza vaccine uptake in health care workers. The researchers used a cross-sectional survey on all of the staff of two Liverpool hospitals who were on the ward at the time of the morning or afternoon change of shift. They ended up using 133 staff members for the study. The results from the survey showed that the number one reason why health care workers who did not get the influenza vaccine (37/133) were because they did not think it was needed. The second reason was that they were not aware of the vaccine (23/133). Other reasons included that they just ‘did not want it’ (18/133) and that they were concerned about the side effects (14/133). Participants identified that they felt the number one benefit of the vaccine was that it decreased sick leave (46/105). In conclusion, many healthcare workers demonstrated a lack of awareness and understanding of the vaccine, especially in relation to its benefits and side-effects. This study was weak because it was not helpful in regards to the influenza vaccination and had limitations including regional bias and a small sample size.

Table 1. Summary of review of literature

Synthesis

The nine research articles we studied all were in agreement that the influenza vaccination is effective. There was no contradicting information. It was shown throughout the articles that the influenza vaccination is most effective for the elderly population, and is beneficial for younger individuals as well. The influenza vaccine was shown to be effective in reducing morbidity and mortality as well as days missed from work, visits to the physician’s office, and hospitalization. It was also shown that getting the influenza vaccination resulted in cost savings. Another thing shown in many of the articles was that there was a lack of awareness in regards the effectiveness of the influenza vaccine. From our research we also concluded that the intranasal vaccination and naturopathic prevention for influenza were not as effective as the actual influenza vaccination. Out of the articles we reviewed, only two of them were prospective trials. It would have been better to have more prospective studies because prospective studies have more control over the extraneous factors and the researchers assign the study factors to the subjects. In the retrospective studies, the data either already existed or a survey was done which is not the most reliable source.

Limitations

Some of the limitations that occurred in these studies included regional bias, relying on the subject’s interpretation of data, and small sample size. The reason that relying on the subject’s interpretation for information occurred was because a lot of the articles we found used retrospective, cross-sectional studies, which limits the researcher’s ability to control factors. Some of the articles did have an adequate sample size, but a couple were lacking in numbers which causes the results to not be as accurate.

Implications for Practice

We can conclude from these research articles that the influenza vaccination is effective. One of the reasons a lot of individuals do not get the vaccination is because they are not aware of the benefits it has to offer. As nurses it is important to educate all patients, especially the elderly population about the benefits the influenza vaccination has to offer.

Discussion

Questions and areas for further study

Some questions that remain unanswered from the research we found include how effective the vaccination is in children, individuals that are immunocompromised, and health care workers. As we were searching for articles the majority of the research we found was done on the elderly population so it might be good for future studies to focus more on other individuals like children, immunocompromised, and health care workers. Also, the studies that included younger populations had such a broad range of ages that it was hard to tell how truly effective the vaccination actually is for younger adults. It would be a good idea for a study to just focus on an age range from around 20-30 years of age to really see how effective the vaccine is for that population.

Considerations for research on this topic

Research on the influenza vaccination has been going on for several years, and there are not too many things that have to be considered when studying this topic. But, something that should definitely be considered when studying the influenza vaccination is that each year the vaccine is different. Therefore, the effectiveness of the vaccine will be different each year. It is good to keep in mind that this vaccination is characterized by annual effectiveness.

References

Bodkin, C. & Klopper, H. C. (2003). Self-care practices and the need for influenza vaccination in healthy individuals. International Journal of Nursing Practice, 9, 382-288.

Canning, H., Phillips, J., & Allsub, S. (2004). Health care worker beliefs about influenza vaccine and reasons for non-vaccination- a cross-sectional survey. Journal of Clinical Nursing, 14, 922-925.

Crocetti, E., Arniana, S., Bordoni, F., Maciocco, G., Zappa, M., & Buiatti, E. (2001). Effectiveness of influenza vaccination in the elderly in a community in Italy. European Journal of European Epidemiology, 17(2), 163-168.

Drake, M., Hauge, M., Lind, A., Magnan, S., Margolis, K. L., McFadden, R., Murdoch, M., et al. (1995). The effectiveness of vaccination against influenza in healthy, working adults. The New England Journal of Medicine, 333, 889-893.

Mangtani, P., Cumberland, P., Hodgson, C., Roberts, J., Cutts, F., & Hall, A. (2004). A cohort study of the effectiveness of influenza vaccine in older people, performed using the United Kingdom General Practice Research Database. Journal of Infectious Disease, 190, 1-10.

Mayo, A. M., & Cobler, S. (2004). Flu vaccines and patient decision making: what we need to know. Journal of the American Academy of Nurse Practitioners, 16(9), 402-410.

Nichol, K. L., Nordin, J. D., Nelson, D. B., Mullooly, J. P., & Hak, E. (2007). Effectiveness of influenza vaccine in the community-dwelling elderly. The New England Journal of Medicine, 357(14), 1373-1381.

Nichol, K., Margolis, J., Wuorenma, J., & Von Sternberg, T. (1994). The efficacy and cost effectiveness of vaccination against influenza among elderly persons living in the community. The New England Journal of Medicine, 331(12), 778-774.

Nichol, K., Mendelman, P., Mallon, K., Jackson, L., Gorse, G., Belshe, R., Glezen, et al. (1999). Effectiveness of live, attenuated intranasal influenza virus vaccine in healthy, working adults. Journal of American Medical Association, 281(2). 137-144.