Recent debate surrounding the efficacy of vaccinations has sparked controversy regarding the effectiveness and safety of mass vaccination programs. This dispute in society has led to the misconception that vaccines can cause severe side effects including illness, disease and death. (WHO, 2019) The outbreak of distrust in vaccines has left the concept of mass vaccination programs eradicating infectious diseases deemed infeasible.
Mass immunisation involves delivering immunisations to a large number of people at one or more locations within a short interval of time. (Grabenstein JD & Nevin RL, 2006) Mass vaccination programs are implemented to maximise the health of population in a safe and ethical manner. Infectious diseases are disorders caused by organisms such as bacteria, viruses, fungi or parasites. (Mayo Clinic Staff, 2019) According to the World Health Organisation, eradication of an infectious disease is considered to be < 1 case of the disease per million of the population. For the purpose of this investigation, eradication will abide by the previous definition.
The varicella-zoster virus (VZV) belongs to the virus family of Alphaherpesvirinae and is commonly referred to as “chickenpox”, is an infectious and highly contagious disease. Varicella (varicellovirus human herpesvirus 3) occurs worldwide and in unvaccinated populations, is predominantly a childhood illness with more than 80%–90% of the population in temperate countries developing clinical infection by adolescence.
The eradication of an infectious disease would rely heavily on a decrease in incidence rates and reported cases of the disease. Therefore, to measure the effectiveness of a vaccination program, there must be a substantial decrease in reported cases of that disease following the introduction of the vaccine to the population under surveillance.
The varicella vaccination program was introduced to the United States in March 1995. Thus, to narrow the scope of this investigation, the incidence rates and number of reported cases of varicella in the United States after the introduction of the varicella vaccination program will be explored.
A study conducted by the American Medical Association (AMA) in 2002 investigates the varicella disease after the introduction of the varicella vaccine program in the United States in 1995. The study mainly measures the outcomes of the vaccination through the rate of varicella cases (incidence and reported cases) and varicella vaccine coverage. The investigation summarises trends in the varicella disease as well as the uptake of the varicella vaccination in the focus surveillance areas (Antelope Valley, California; Travis County, Texas and West Philadelphia, Pennsylvania) from January 1, 1995 through to December 31, 2000.
At all sites, the amount of reported cases declined in 1996 after the implementation of the varicella vaccination program. The initial decline remained relatively stable up until 1998 where there was considerable decline. Over the three locations, there were significant declines in the number of reported and verified varicella cases with Antelope Valley decreasing from 2934 to 837, Travis Country decreasing from 3130 to 491 and West Philadelphia decreasing from 1197 to 250. Overall, the rate of the disease throughout each controlled area experienced a significant declined in all age groups following the introduction of the varicella vaccine in March 1995. Since the introduction of the varicella vaccine, there has been a substantial decrease in the number of reported cases of varicella across all age groups as March 1995 marks the beginning of this ample decline indicating the feasibility of eradication if these results were to project into the future.
A limitation of this evidence is the fact that varicella, in these locations, from 1995-2000, has an apparent seasonality, with the largest number of cases being reported and verified during the months of March, April and May. In December 2000, towards the end of the study, there is a slight increase in the number of reported cases of varicella which disrupts the general trend of the results recorded prior to this minor anomaly, despite seasonality. Since these results end after the introduction of the slight increase, it is difficult to conclude whether the remaining data starts a new trend or continues the previous trend. Other figures and tables used in the study were deemed either statistically significant or not statistically significant, however, this evidence did not receive the same statistical analysis.
‘Varicella Disease After Introduction of Varicella Vaccine in the United States, 1995-2000’ recorded by the AMA in 2002 also compared the overall reduction of the reported cases of varicella from 2000 and 1995 to support the evidence.
Antelope Valley, Travis County and West Philadelphia all experienced a significant reduction of varicella cases of 71%, 84% and 79% respectively. The study claims that to be able to demonstrate the decline of a disease in a community, not only does the vaccine need to be effective, but it be distributed at a high enough level to induce a marked decline in the incidence of the disease. The evidence provided in Table 1 clearly demonstrates the significant decrease in the number of reported varicella cases. The data from the post licensure study supports the decline of varicella transmission and solidifies the decline in the incidence of varicella following the introduction of the varicella vaccine program in 1995.
A limitation regarding Table 1 includes the fact that the table is described to compare 1995 varicella incidence to 2000 varicella incidence, however, the table only includes an individual figure that represents the percentage reduction between the two periods. Providing separate values for each year and age group would assist to develop validity within the study. Table 1 has been sourced from the same study and has not received the statistical analysis that other figures and tables in the study had underwent. It is not stated whether these results are statistically significant or not statistically significant.
In 2019, the Infectious Diseases Society of America (IDSA) conducted a study investigating the impact that the introduction of the varicella vaccination had on the incidence of varicella and herpes-zoster in the United States. Data from Observational Databases, such as Medicare and Marketscan Commercial, 1991-2016 were utilised. The study concluded that the impact that the introduction of the varicella vaccine had on the reduction of the varicella disease was substantial.
The evidence depicts a strong decline in the incidence per 100,000 population of varicella over an approximate 10 year period, across all age groups. clearly shows the significant impact that the implementation of the varicella vaccination program has had on the United States population that could potentially adopt and transmit the disease. Since the introduction of the varicella vaccine, there has been a substantial decline in the incidence of varicella across all age groups as there is a marked decline in 1995, demonstrating that the varicella vaccination program in the United States has directly resulted in this decline.
A limitation is the fact that the study conducted no statistical analysis, therefore, it is not stated whether the results are statistically significant or not. A further limitation is the fact that it is sourced from a study that does not focus solely on the incidence of the varicella disease. Although it contains evidence of the varicella vaccine program’s impact on the disease, most of the paper explores the incidence of herpes-zoster and provides virtually no discussion of the results, restricting the reliability of the evidence.
The evidence contributed by the study conducted by the AMA gives insight into the reduction of the number of verified, reported cases of the varicella disease succeeding the introduction of the varicella vaccination to the United States. The study revealed a strong correlation between the two variables; the implementation of the varicella vaccine in the United States and the decline of the number of reported cases of varicella.
The IDSA study on the impact of the varicella vaccine on the incidence of the varicella disease reveals that the incidence of the varicella disease has declined significantly following the introduction of the varicella vaccination program in the United States.
Although each study has limitations, the findings of both studies are sourced from medical associations representing healthcare professionals and physicians that specialise in infectious diseases and or public health, therefore, provide reliable and valid data that responds directly to the research question generated. An educated conclusion can be drawn that since the United States introduced the varicella vaccine, the incidence rates and number of reported cases of varicella-zoster virus have, in fact, declined.