The Effects of Vaccination in Case of Influenza on the Elderly in Hong Kong in Reducing Flu Infection

The reason for this dissertation is to establish the effects of vaccination on the elderly (>65 years old) in Hong Kong in reducing flu infection. Influenza vaccine uptake in the elderly (˃65 years old) in Hong Kong significantly increased in 2003 after the SARS epidemic. The exact impacts of influenza vaccine among the elderly in Hong Kong are a subject of contention. The effectiveness of the influenza vaccine comes from observed studies which may be prejudiced since it is difficult to identify and justify the evidence. A review of various literatures has shown that influenza causes serious illness and death particularly highly vulnerable groups such as adults aged 65 years and above. Therefore, more efforts should be initiated to reduce mortality caused by influenza among the elderly. According to the WHO (2005), vaccination is among the most effective approach for preventing death associated with influenza to vulnerable groups such as the elderly.

birds, horses, swine, and so forth, and it presents a risk to human beings. Type A influenza virus has been linked to various pandemics and the highest morbidity and mortality rates. Both Type B and Type C viruses cause infections in people only. Type B influenza is the same as Type influenza. According to clinical presentation Type, A influenza usually affects young adults and children. Influenza Type C is modest and does not result in infections or epidemics but can cause mild respiratory infections in both adults and children.
Type A influenza causes a lot of pandemics and comprises haemagglutinin (HA) (H1-H16), 16 glycoproteins, and 9 neuraminidase (NA) (N1-N9) subtypes that were extracted from birds, sea mammals, horses, pigs and humans (Horimoto & Kawaoka 2005). Three subdivisions of HA type (H1, H2, and H3) have been found among humans. Influenza B generally happens between two to four years. Type C Influenza is usually related to periodic and subclinical infections. The 1918 Spanish influenza was caused by the first subdivision of the H1N1 virus.
The next subdivision H2N2 was responsible for the 1957 Asian influenza comprised of PBI (polymerase basic 1), HA (H2), and NA (N2). The third subdivision H3N2; H3N2 which has HA (H3) and PBI division in the background of the human gene caused the 1968 Hong influenza.

Modes of Transmission
Understanding the mode of influenza transmission and the period of infections are vital factors of control measures such as vaccination. Influenza virus reproduces in the epithelium of the respiratory tract; penetrates the body through the nose and mouth. Infected hosts can discharge virus into the air during sneezing, coughing, talking and breathing producing particles which are of different sizes. Three paths of transmission well known include droplet which is large particles and can fall on the upper respiratory tract but due to the size, they cannot be transferred into the lungs (Zhang et al. 2018). Aerosol and small particles that can remain hanging in the air for longer duration and they can land into the lower respiratory tract. This droplets nuclei causes severe illness. Contact transfer involves the transfer of contagious particles to other membranes through direct contact of contaminated objects. Sometimes it can be transferred through indirect contact of contaminated objects. More research should be conducted to completely explicate the epidemiology of the spread of certain ARIs from one elderly to another especially those in care homes in Hong Kong (Wong et al. 2004).

Droplet and aerosol transmission
The significance of these routes of influenza spread is not well known and the involvement of aerosolized contagious droplets of nuclei has been a debate of contention.
Droplets with the diameter of ˂8µm comprise more than 99% of the spray during cough; therefore, coughing can produce a lot of small particles. However, their volume is low and most of the virus particles are infected in larger droplets that do not scatter extensively hence proximity is needed for transmission to occur. Although studies done by Gupta, Y.K. & Padhy, (2010) established that influenza viruses can survive artificial airborne aerosols for some time, the importance of their studies about the natural routes of influenza infection has been doubted by other researchers. Disease transmission through aerosols is affected by host factors such as viral load, site infection, respiratory activity, and incidences such as particle aggregation, evaporation, and relative humidity. However, the direct confirmation that naturally developed aerosolized particles can endure the journey and reach the susceptible hosts and transmit disease is wanting. More research on the transmission of influenza virus is required. An aerosolgenerating process is described as a medical process that can stimulate the production of aerosols into different sizes such as droplet nuclei.
Studies on the epidemiology of influenza transmission have overlooked to address the spread of the virus from one elderly to young health care workers during the aerosol-generating process, especially in regards to other pathogens. This gap arises because different kinds of literature fail to fully define the aerosol-generating process. Additionally, there is insufficient information concerning the minimum ventilation requirement to minimize pathogen spread during these processes. There is no confirmation to indicate a difference in the efficacy of particulate respirator on face masks as a constituent PPE for regular care. However, further research is required to establish if there is a difference between medical masks and the efficacy of particulate respirators in regards to the aerosol-generating process that has been constantly linked to the risk of pathogen transmission. The different medical intervention involves in a risk of generating aerosols, which has outcomes for the recommendations for infection control and personal protection measures. Kwong et al (2010) performed a methodical evaluation of 10 nonrandomized types of research that appraised the risk of transmission of severe infections to elderly in a hospital set up in Hong Kong undergoing aerosol-generating processes compared to those not undergoing the process. The study found a considerably increased risk of transmitting an acute respiratory syndrome among those that did receive the influenza vaccine.

Influenza Symptoms
Influenza (flu) is explained as an infectious, respiratory sickness caused by influenza viruses. It is responsible for the upper and lower respiratory tract infections which include throat, nose, and lungs. At times, such infections can be mild, extreme, and even result in the death of the patients. Signs and symptoms of influenza consist of cough, running nose, headaches, body aches, chills, muscle aches, fever, stuffy nose, fatigue, and feeling nauseous. Diarrhea and vomiting are more prevalent among children (CDC 2013).

Vaccine types
Influenza vaccination is considered to be the most effective way of preventing influenza, complications associated with the flu and helps to reduce influenza-associated hospitalization and mortality. The current registered Seasonal Influenza Vaccines (SIVs) in Hong Kong comprises live attenuated influenza vaccine (LAIV) and an inactivated influenza vaccine (IIVs).  During the peak influenza season, the elderly are more susceptible to influenza. Therefore, elderly people are considered to be a risk population because the population is generally aging and will increase extremely in the coming years. This results in the prevention measures to contain the disease and the government has given this population a priority.
However, it is a costly measure for health care facilities to offer treatment to this population which makes the government adopts prevention. The government advised people to observe key prevention measures like hand washing, wearing face masks, using antibacterial sanitizers, and

Efficacy and effectiveness of influenza vaccines
Vaccination is among the most effective public health tools presently available to protect people from influenza infections. Vaccine effectiveness (VE) is determined by the relationship between virus strains available in the vaccine and the virus spreading in a particular community. Some studies have indicated that when strains in IV tend to match with those circulating, vaccinated people are 60% less likely to get the flu compared to those who are not Early estimates of influenza vaccine efficacy by Wong et al (2004) suggested that influenza vaccines were 80 % effective in reducing flue infection among the elderly. However, the real effectiveness of the influenza vaccine has been discussed by different researchers. Two meta-analyses study by Leung (2007) revealed much lower efficiency than initially believed. All meta-analyses showed that administering the influenza vaccine in the elderly such as the MF59adjuvanted influenza vaccine was effective for averting hospitalization because of influenza or pneumonia-related complications although its effectiveness ranged from 40 to 50%. One metaanalysis comprised only community elderly persons in Hong Kong, while the other also incorporated institutionalized elderly persons. The outcomes of the previous reviews indicated that the effectiveness of hospitalization due to influenza was higher in the institutionalized elderly 36 to 47% compared to community based elderly 25-33%. Although the meta-analyses and other studies showed significant effectiveness for preventing hospitalization associated with influenza, most research findings included other severe acute respiratory infections (SARI) and failed to concentrate on influenza only. Additionally, most studies were undertaken when in the previous years when influenza vaccine intake was still very low and antiviral agents were limited. In the current context, which has high rates of influenza vaccine uptake, the herd effect can be very significant. This means that early treatments and vaccinations can reduce the possibility of influenza infection among the elderly in Hong Kong. More studies are needed to understand clearly how the influenza vaccine is important to the elderly in the modern context, described by high vaccine intake.

Observational studies
Most studies used different types of observational studies such as case-control and cohort studies. The pieces of literature evaluated how influenza vaccines work among the elderly by drawing a comparison between those who had been vaccinated against those not vaccinated.
Vaccine effectiveness is described as the reduction level in the occurrence of influenza illness in vaccinated people in comparison to those that are not vaccinated, typically with alteration factors that are related to influenza sickness and vaccination. The adjustment factors include the existence of severe medical conditions. In the meta-analysis, influenza vaccination rates were above average. The studies indicated that influenza vaccination was effective among the elderly.
A good number of observational studies showed an increase in influenza vaccine effectiveness in elderly people with primary health conditions.

Randomized controlled trials (RCTs)
This kind of study design is where participants are assigned arbitrarily to get the

What is known in the literature?
It is believed that the influenza virus is the major cause of mortality and morbidity.
Alders are considered people at higher risk because the disease presents serious complications that lead to hospitalization and even death. During the peak influenza season, the elderly are more susceptible to influenza. Therefore, elderly people are considered to be a risky population because the population is generally aging and will increase extremely in the coming years. This results in the prevention measures to contain the disease and the government has given this population a priority. According to the WHO, vaccination is among the most effective approach for preventing death associated with influenza to vulnerable groups such as the elderly. The