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Vaccines: One of Public Health's Biggest Achievements

Vaccines: One of Public Health's Biggest Achievements

Start a Public Health degree at American Military University.

By Dr. Jennifer Sedillo
Faculty Member, Public Health, American Military University

World Immunization Week occurs during the last week of April and is used “to promote the use of vaccines to protect people of all ages against disease.” In public health, vaccinations are the most cost-effective, safe methods to prevent and control infectious diseases. While vaccines continue to be the best method for controlling infectious diseases, there have been setbacks in the progress made to preventing life-threatening diseases.

Defining the Difference between Vaccines and Immunizations

The term vaccine and immunization are often used interchangeably. Immunization implies that the vaccine has worked to create immunity in the vaccinated individual. The vaccine is what is injected into the individual to stimulate the immune response, typically a protein or whole cell.

Vaccines Typically Used at Different Stages in Patients’ Lives

Different vaccines are critical for different stages in life. The Centers for Disease Control and Prevention (CDC) recommends routine vaccinations for children in the United States, based on the recommendations of a panel of medical and public health experts, the Advisory Committee on Immunization Practices (ACIP).

Vaccines are recommended by the CDC for specific age groups based on their proven safety and effectiveness. For example, there are 14 vaccine-preventable diseases where immunizations are recommended during childhood, with an additional four vaccinations available for children and young adults ages 7-18.

Because a young child’s immune system is still developing, some vaccines are not effective until later in life. If the child is at risk of specific diseases, vaccinations may be offered earlier in his or her life.

Despite publications by non-regulatory organizations, there is no recommended alternate vaccination schedule in the U.S. The CDC publishes “catch-up” schedules for those who miss childhood vaccinations so that they can safely and effectively receive the necessary immunizations. However, some countries have different vaccination schedules, based on the threats of certain diseases in their geographic location.

Vaccine Setbacks and Challenges

Outbreaks of vaccine-preventable diseases can be found globally. But in developed countries, this is typically not the case. In fact, the last few years have seen resurgence of vaccine-preventable diseases across the U.S. and in other areas.

For instance, measles vaccination in Europe and the Americas has decreased, which has led to the disease coming back although it was eliminated from the Americas over a decade ago. Recent measles outbreaks such as in Clark County, Washington and Rockland County, New York, for example, highlight that reduced vaccination among the public leads to outbreaks as the measles virus continues to circulate globally.

In response to the outbreaks, the CDC has launched health campaigns to hopefully reduce unjustified fears of the vaccine and to counteract the misinformation that has led to vaccination rate reduction. Measles is a solely human disease that is passed from person to person. It is proposed that high enough vaccination rates can lead to complete eradication of the disease, like smallpox in the 1970s.

Another disease, whooping cough (pertussis), has also increased in incidence recently. However, the reappearance of whooping cough is not due to reduced vaccination rates, but instead to waning immunity against the disease.

Current research is looking into whether the type of vaccine now used, an acellular version that replaced a dead whole cell version, produces a shorter-term immunity to whooping cough or if the vaccine is losing effectiveness due to mutations in the bacterium that causes the disease, leaving the vaccine less effective. The CDC now recommends that adults receive boosters of this vaccine to reduce risk.

Similarly, the Hepatitis A virus has recently caused large outbreaks across the U.S., mostly among homeless populations and injection drug users. This disease is typically foodborne, but may also be spread person to person. Aggressive vaccination campaigns such as the one launched in San Diego have helped to quell the outbreaks.

The Hepatitis A vaccine is a recommended childhood vaccination in the U.S., but has only become so since 1994. Consequently, many adults are not vaccinated for this disease and may be at risk.

Global Challenges to Regular Vaccinations

Globally, the challenge of vaccines is accessibility. Many impoverished parts of the world struggle to afford vaccines as well as the healthcare infrastructure and workforce to promote large-scale vaccination efforts.

Furthermore, populations that are either displaced or migratory may not be accessible to healthcare workers to ensure proper vaccinations. In many parts of the globe, populations have a distrust of governments and foreign aid workers, which also leads to a lack of vaccination coverage. Furthermore, many diseases that cause significant morbidity and mortality worldwide do not have well-developed vaccinations and therefore continue to burden populations.

Eradication of Polio Is Currently a Global Public Health Goal

The eradication of polio (poliomyelitis) worldwide is a current public health goal at the global level. Polio can be eradicated through aggressive and thorough vaccination campaigns, as seen with two of the three main types of polio that have been eradicated due to public health vigilance.

However, vaccination coverages in countries that have optimal conditions for transmission continue to be low and result in vaccine-derived cases of polio in a community. If herd immunity is present where a high percentage of the population is vaccinated, the virus will not be able to survive without susceptible hosts. As a result, both the wild-type and vaccine-derived forms will no longer exist.

While most countries are polio-free, 15 countries are still at high risk and three countries have currently circulating poliovirus: Pakistan, Afghanistan and Nigeria. Great reduction in cases has been seen with only 22 cases reported in 2017, but full eradication can only come when transmission stops worldwide.

Malaria and Ebola Virus Remain Global Problems

Malaria is a disease transmitted by a mosquito that is responsible for hundreds of thousands of deaths worldwide and millions of cases each year. The disease is complex both in terms of biology and sociopolitical factors.

Ninety percent of deaths occur in sub-Saharan Africa where poverty is high. A vaccine (RTS,S/AS01) has been developed and is being piloted in high-risk areas. It is used to prevent severe malaria and hopefully save lives, but the vaccine does not meet the intended goal of effectiveness “at least 75% against clinical malaria for areas with ongoing malaria transmission.” Other vaccine candidates are undergoing clinical trials but more development is needed for an effective malaria vaccine.

The Ebola virus has come out of the shadows and has caused recent large epidemics; one continues to surge on today in the Democratic Republic of Congo. The virus quickly causes death and there is no known cure, making it a prime candidate for vaccine development.

Vaccines for the Ebola virus are in early-stage clinical trials, but vaccine development suffers from some of the same issues as malaria vaccine development, where the burden of disease falls on the most impoverished parts of the world that cannot afford the expense of vaccine development. Foreign companies and agencies are working to develop an Ebola vaccine, but clinical trials to demonstrate safety and efficacy are time-consuming and come at a high cost.

Vaccine Development Successes with HPV and Cholera

The human papillomavirus (HPV) is responsible for 99% of cervical cancers in women. The HPV vaccine was developed in 2006 to prevent cervical cancer in women, genital warts and HPV-related cancer in men.

During clinical trials, it was found to have a high efficacy rate.  The HPV vaccine provides almost 100% effectiveness against the HPV types included in the vaccine, which cause the most cancer and genital warts. Other types are less likely to cause cancer and other symptoms. Currently, several versions of the HPV vaccine are licensed and used to prevent cervical cancer and other communicable diseases.

Cholera is a bacterial disease that is spread through fecal-contaminated water and food. Cholera outbreaks typically occur after societal disruption that causes a humanitarian emergency, such as after the devastating earthquake in Haiti or the civil war in Syria.

The cholera vaccine has been widely used since 1997, but its use in response to large outbreaks was questioned until recently. Studies conducted during these emergencies showed that the vaccine is a critical part of outbreak response.

In 2013, the World Health Organization created a stockpile of this vaccine for countries and it is recommended for use to reduce the fatality rate of this disease. Together, it is estimated that vaccines have saved over 10 million lives and prevented numerous lifelong disabilities in a five-year span.

An Interconnected World Means that We Need to Work Harder on Finding Cures for Diseases

Our world is interconnected thorough travel, migration and the global supply chain, so infectious diseases are easily spread from one country to another. Vigilance in the form of disease surveillance and public health interventions are needed to prevent infectious diseases in the U.S. and abroad. Vaccines provide a potent way to prevent diseases, which is always a safer and more cost-effective way than a cure.

Do your part to help stop the spread of communicable diseases throughout the world and get regular vaccinations as recommended by your physician. You could help a child in a country where vaccinations are not accessible, simply by doing your part to keep you and your family up to date on vaccinations.

About the Author

Dr. Jennifer Sedillo is an Associate Professor in the Public Health Program at AMU. Her background is in microbiology and molecular biology of infectious diseases. Her doctoral dissertation focused on the pathogenesis of the malaria parasite. Jennifer has co-authored several papers focused on disease pathogenesis of microorganisms. She continues to be fascinated with microorganisms and how they can be both beneficial and harmful to humans.