Adult immunization-Need of the hour.

Immunization is the process or the act of making individuals immune, which is usually done during childhood. Everyone is aware about immunization during childhood, however, very few know about adult immunization. This led us to review the adult immunization literature for the preventive strategies through various vaccination protocols. Adults do require vaccination protocols with booster doses for hepatitis B, Shingles, communicable diseases, traveler's diseases, etc. In this context, this article revises much of the available adult immunization literature and presents comprehensive guidelines. This article will increase the awareness regarding the importance of vaccination for adults to prevent a variety of conditions prevalent in our country as well as epidemics. The article comprehensively provides insights into the available vaccination and preventive strategy of human papilloma virus (HPV), hepatitis, and human immunodeficiency virus (HIV) infection in this part of the review. We strongly recommend all the health care professionals to educate their co-professionals and the public to use the benefits of adult immunization. It is the need of the hour and reduces the burden of treatment and increases productivity.

INTRODUCTION

Vaccinations or immunization is of great importance for public health and is the success story of the 21st century. Immunization or vaccination is the prime mode for the prevention of diseases among infants and children to prevent mortality and morbidity. Elimination of deadly diseases can be prevented successfully through immunization or vaccination. Vaccination is an important part of public health programs all over the world. The most recent success story in India is the eradication of polio. The prevention is not only relevant for children and infants but also for adults. In the elderly population, because of the changing demographics and significant increase in the life expectancy, the concept of adult immunization was thought of. Vaccination of adults should become a new national health priority because of the economics involved in disease treatment. Immunization minimizes morbidity and mortality, which is time tested. Promoting lifestyle through the prevention of disease, early detection, and prompt management are going to help in longevity of life. Unfortunately, adult immunization remains untapped in India. Data on adult vaccination is still scanty. This article reviews the principles and technical aspects of vaccination. The emphasis of this article is on special classes of people such as pregnant women, immigrants, and travelers. The article focuses on newer vaccination on hepatitis, including the recommendation for the Indian population. This comprehensive update will provide evidence-based practice guidelines for vaccination strategy in the Indian population.

Several diseases are still a major health problem in India, as well as in other developing countries. The burden of diseases and reliable epidemiological data in regards to infectious diseases are still lacking. Keeping this in mind, the literature search for adult immunization for various diseases such as anthrax, cancer, chikengunya, cholera, dengue fever, hepatitis, influenza, human papilloma virus (HPV), malaria, and leprosy was carried out and comprehensively reviewed for HPV, hepatitis, and human immunodeficiency virus (HIV) infection in this section of the review.

NEED FOR ADULT IMMUNIZATION

A major public health concern among adults is the prevention of health complications, which is a serious matter and sometimes potentially fatal. Therefore, immunization is the prime mode of prevention. The approaches to adult immunization is through raising awareness among the public and professionals. The administration of immunization has to follow certain guidelines toward patients, type of vaccines, route, site, and dose of administration. The documentation is important for vaccination, which includes the date of administration, name of the vaccine, and date for booster doses, with the signature of the authorized personnel. One should provide the knowledge about vaccine services and trusted health care professionals for mass vaccination program.[12] Immunization is of two types, namely, active and passive. The immunization strategies and basics of immunization can be read elsewhere.[345]

The world health organization (WHO) is involved in the prevention of major communicable diseases. The WHO and United Nations Children Emergency fund (UNICEF) consider 10–19-year-old individuals as adolescents. This adolescent group is more vulnerable toward many communicable diseases and requires special attention. Reproductive age group plays a significant role in determining the future of India, even though they might have been vaccinated during their childhood. Because of the shift in epidemiological diseases among the adolescent age group, many developed countries have introduced immunization guidelines.

Concepts of immunization of adolescents

The concepts have been developed for proper vaccination coverage for adolescents. Immunization for adolescence is recommended as a routine and follow-up before administering vaccines. It is necessary to complete any incomplete vaccination prior to affliction with diseases, which can be prevented through vaccination. Patients should be enquired about other conditions, previous adverse effects, and allergies. This will also reveal lifestyle practices that will help health care professionals in prevention.

HUMAN PAPILLOMA VIRUS VACCINE

The burden of HPV in the Indian population is associated with oncogenic HPV, which includes cervical, oral, vaginal, pineal, and oropharyngeal cancers, ranging from 100 to 40%.[6] Respiratory papillomatosis is rare but preventable through vaccination.[7] Four hundred thirty two million Indians of 15 years as well as older women are at a risk of developing cervical cancer. Based on Indian studies, in general, HPV detection in cervical samples is 7.9%. HPV16 or HPV18 contributes to to 84.1% of cervical cancer.[89] High prevalence of the association of HPV types 16, 18, 31, 33, 35, 45, 52, and 58 are designated as high risk.

Need for human papilloma virus vaccine

The prophylactic HPV vaccine has been used for primary prevention of cervical cancer and other HPV-associated diseases.[10] HPV is a common sexually transmitted disease. The vaccination will reduce the burden of HPV-associated cancers, including subsequent risk reduction among women, as well as young men to reduce the risk of HPV infection. The vaccines available for prophylaxis are bivalent HPV (BHPV) and quadrivalent HPV (QHPV). Both are effective against precancerous lesions and type 6, 11, 16, and 18 viruses. The future of HPV vaccine is gaining importance. The two dose schedule has been tested,[1112] and one more randomized trial has been tested for three doses.[13] Quadrivalent vaccine is recommended against HPV for males aged between 11 and 21 years. Catch up vaccine is recommended for 13 to 21 year old individuals. In addition, routine use is recommended for males aged between 20 and 26 years who have had sexual contact with HIV-positive individuals.[14]

Recommendation for human papilloma virus vaccination

BHPV and QHPV are licensed for use in female and one HPV for use in males. For females, HPV4 and HPV2 is recommended in three dose series.[15161718] Routine vaccination should be administered to females at an age of 11 or 12 and those aged between 13 and 26 years, if not vaccinated previously.[15161718] For males, HPV4 in three doses at the age of 11 or 12 years and those aged between 13 and 21 years, if not vaccinated previously.[15161718] Males aged between 20–26 years may be vaccinated. The vaccine recommended for immunocompromised patients including HIV infection through the age of 26 years, the series of HPV4 or HPV2 consist of three doses.[15161718] The second dose should be administered 1 or 2 months after the first dose and the third dose after 6 months of the first dose.[15161718] In India, the academy of pediatrics recommends initiation for vaccination at 10–12 years and catch up is permitted up to 45 years.[19] The obstetrics and gynecology society of India recommends 10–12 years for females permitted till 45 years.[20] The physician association of India indicates QHPV vaccine for women aged 9–45 years.[21] Bivalent vaccine is for women aged 10–45 years as well as for cervical cancer patients caused by HPV16 and HPV18.[22] Both the vaccines are given in three dose schedule.

CHANGING PARADIGMS IN HUMAN IMMUNODEFICIENCY VIRUS

Acquired immune deficiency syndrome (AIDS) caused by HIV is prevalent in India with 2.5 million affected people.[23] Even with the advent of antiretroviral drugs for the treatment of HIV, it continues to be one of the most communicable infections. The development of HIV vaccine has few obstacles.[24] However, in 2009, in Thailand, the vaccine trial was completed with 31% efficacy.[2425] India is in an urgent need of vaccines because of the high burden of opportunistic infections. The development of a vaccine has major limitations because of the highly mutagenic genetically variable subtypes, lack of suitable animal model for vaccine development, and limited natural response to the virus. Lack of clear correlation of protective immunity to the viral components is entirely unknown; these factors cause the difficulty in the development of vaccines. The challenges posed by HIV virus prove difficult to develop a vaccine. The present scenario of HIV vaccine is still under a trial phase.[2627282930] The partial success of RV144 vaccine has provided a much needed impetus. India hosts the third largest pool of HIV-positive patients, and hence there is an urgent need for vaccination. National AIDS research institute and tuberculosis research center have conducted phase-1 trials in Pune and Chennai, respectively. All the volunteers followed for one year after booster dose administration were well tolerated. Availability of a large pool of patients and unique molecular epidemiological profile attracted many organizations for vaccine initiative. All the conventional vaccine development methods have been used to develop an effective vaccine. The partial success of the vaccine provided some hope for future success. The current vaccine is in the experimental stage, which will take a long time before it is available in the market.

CURRENT STRATEGY OF HEPATITIS B VACCINE

Hepatitis B vaccine (HBV) is indicated for universal immunization, adults, and high risk groups who have missed HBV vaccination. HPV elimination is possible through universal vaccination of an infant at birth. Prevention of perinatal infection through screening of pregnant females, vaccination of children, adolescent inmates, staff of developmentally disabled individuals, unvaccinated adults, drug abusers, and household contacts.[31323334]

Recommendation for hepatitis B vaccine

Individuals at risk by sexual exposure. HBSAg positive sex partners, sexually active personnel, homosexual (males), and individuals seeking treatment for sexually transmitted diseases

Individuals who are at risk for infection by percutaneous injections and mucosal exposures to blood. Drug users, household contacts of HBSAg positive persons, residents and staff of facilities for disabled persons, health care and public safety workers, persons with end-stage renal diseases, and individuals requiring blood transfusions

Individuals with chronic liver diseases, HIV infection, and all individuals seeking protection from HBV virus.

Recommended schedule

In the Indian scenario, 20 µg at 0, 1, and 6 months and immunocompromised 0, 1, 2, and 12 months. Double the dose of 40 µg in chronic renal failure, renal transplant, post-transplant, and hemophilia. Anti-HBV titers should be estimated 1–2 months after the last date of vaccination. If it is less than 10 mIU/ml, a booster dose is required. In nonresponder of HBSAg, the vaccination should be repeated with a schedule of 0, 1, 2, and 12 months.

HEPATITIS C VACCINE

It affects more than 170 million people globally.[35] India has a moderate prevalence of hepatitis C virus (HCV) infection in general population.[36] Vaccination is needed to prevent or attenuate primary infection. The prophylactic vaccine prevents and the therapeutic vaccine aims to get rid of the infection.

The challenges for the development of a vaccine are posed by antigenic diversity with six genotypes, 30–35% of dissimilarity across the genome, and the need for the vaccine to be genotype specific. Therefore, it is important to identify the antigen against which the vaccine needs to be developed. Lack of proper experimental animal model limits the testing efficacy of vaccines. Currently, four vaccine strategies have been investigated in human clinical studies. These are as follows: Recombinant protein, peptide, DNA, and vector vaccine. Recombinant vaccine is a potential vaccine that will produce an immune response to eliminate a number of viral epitopes, which are efficient to develop protective immunity. In general, protein based approaches induce antibody and CD4+T cell response. Experimental vaccines are safe and well-tolerated with no significant effects. However, larger studies are required to establish safety and cost-effectiveness of the vaccine. In India, research is lacking which needs to be promoted. The impact of disease is high in relation to morbidity and mortality. Therapeutic vaccines are promising but not preventive. Recombinant vaccines of 20 µg at 0, 3, and 6 months are safe and well-tolerated, which stimulate hormonal and cell-mediated immune response.[37383940]

HEPATITIS E VACCINE

Hepatitis E is an important agent transmitted enterally, which causes acute viral hepatitis globally. Fourteen million symptomatic cases with 300,000 lakh deaths and 5200 stillbirths occur annually around the world. Mainly, developing countries such as the Indian subcontinent, Africa, northern, western part, and Middle East are more prone to infection. Recently, in Sudan and northern Uganda, the outbreak of Hepatitis E was reported, which necessitates safe and effective vaccine. In India, during 1955–56, in New Delhi, contamination of drinking water with an outbreak had occurred. Hepatitis E is a hepivirus, genus hepivirus in the family hepeveridy. Hepatitis E virus (HEV) genome consists of four major mammalian genotypes and one avian genotype. Hepatitis E protection is required specifically for pregnant females, cirrhotic patients, and travelers on urgent basis. The epidemiological outbreak necessitates safe and effective Hepatitis E vaccine. Current status of vaccine is the successfully launched hecolin for ® (HEV 239 vaccine), following successful phase 2 and phase 3 clinical trials. The vaccine was tried which gave a shorter duration of immunity and passive immunization with higher titer. HEV antibodies may reduce infection during pregnancy as well as its severity.[41424344]

CONCLUSION

Vaccine administration is critical for the success of immunization. The HPV, HBV, and HEV are currently available for clinical use, however, those for HCV and HIV are still under trial. It is necessary to educate the public about adult vaccination for use of existing vaccines. The vaccine should be made available, should be cost-effective, and delivery should be simple; it should be easy to use in resource limited countries where the disease is endemic. Both health care professionals and the general public have become frequent travelers all over the world because of ease of transportation. Hence, adult immunization has become the need of the hour to prevent transmission of deadly diseases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.