Community Immunity: How Vaccines Protect Us All

Community Immunity

How Vaccines Protect Us All

Parents know that kids are vulnerable to a host of infectious diseases. Research supported by NIH and others proves that the benefits of vaccines in preventing illness and death greatly outweigh the risks.

The list of childhood diseases can be overwhelming: measles, mumps, rubella, diphtheria, pertussis, polio, meningitis, influenza and rotavirus. In the era before vaccines, many children in the U.S. died or became disabled from these diseases. Many still do in countries and regions with lower vaccination rates.

With all the international travel in the world these days, it’s important to keep vaccines, or immunizations, up to date. Here’s just one example of what might happen if you don’t. By 2000, immunization had practically wiped out measles in the U.S. But a measles outbreak in 2005 was traced to one unvaccinated U.S. resident infected during a visit to Europe. The returning traveler infected American children who hadn’t been vaccinated because of safety concerns—despite study after study showing that childhood vaccines are safe and effective.

A major epidemic didn’t emerge that time. That’s because enough people in the surrounding communities had already been vaccinated against measles.

“The important concept,” says Dr. Marc Lipsitch of the Harvard School of Public Health, “is that vaccinating people protects not only them, but others in the community. If I’m protected, I can protect others.”

This type of protection is known as “community immunity” or “herd immunity.”  When enough of the community is immunized against a contagious disease, most other members are protected from infection because there’s little opportunity for the disease to spread.

Newborns, pregnant women or people whose immune systems are weakened may not be eligible for certain vaccines. Yet even they will get some protection because the spread of contagious disease is contained.

“Epidemiologists think of infections as chain reactions, whose speed depends on contagiousness,” says Lipsitch. “The more contagious the disease, the more vaccination is required. The data tells us that herd immunity works.”

Using mathematical formulas and computer programs, NIH-funded scientists like Lipsitch have developed models to determine what proportion of the population has to be vaccinated to eliminate the spread of disease. As one example, a worldwide vaccination campaign completely eliminated, or eradicated, smallpox in the 1970s. So many people were immunized that the virus couldn’t sustain itself.

More recently, infant vaccination against Haemophilus influenzae type b (Hib, which can cause meningitis) lowered the risk of disease in the whole population. Before the vaccine, Hib struck about 1 in 200 children younger than age 5. It killed many and often left survivors with permanent brain damage. After the Hib vaccine was introduced in the mid-1980s, the incidence of Hib dropped by 99%.

“Infectious disease eradication is possible,” says Lipsitch. Even when a disease—such as measles or Hib— hasn’t been completely wiped out, immunizations can reduce disease transmission, so that epidemics become less frequent.

Ingredients of Vaccines

Ingredients of Vaccines

Chemicals commonly used in the production of vaccines include a suspending fluid (sterile water, saline, or fluids containing protein); preservatives and stabilizers (for example, albumin, phenols, and glycine); and adjuvants or enhancers that help improve the vaccine's effectiveness. Vaccines also may contain very small amounts of the culture material used to grow the virus or bacteria used in the vaccine, such as chicken egg protein.

Important Facts

• Millions of doses of vaccines are administered to children in this country each year. Ensuring that those vaccines are potent, sterile, and safe requires the addition of minute amounts of chemical additives.
• Chemicals are added to vaccines to inactivate a virus or bacteria and stabilize the vaccine, helping to preserve the vaccine and prevent it from losing its potency over time.
• The amount of chemical additives found in vaccines is very small.
• All routinely recommended pediatric vaccines manufactured for the U.S. market are available in formulations that contain no thimerosal or only trace amounts.

Common substances found in vaccines include:

• Aluminum gels or salts of aluminum which are added as adjuvants to help the vaccine stimulate a better response. Adjuvants help promote an earlier, more potent response, and more persistent immune response to the vaccine. 
  
  
• Antibiotics which are added to some vaccines to prevent the growth of germs (bacteria) during production and storage of the vaccine. No vaccine produced in the United States contains penicillin.
• Egg protein is found in influenza and yellow fever vaccines, which are prepared using chicken eggs. Ordinarily, persons who are able to eat eggs or egg products safely can receive these vaccines.
• Formaldehyde is used to inactivate bacterial products for toxoid vaccines, (these are vaccines that use an inactive bacterial toxin to produce immunity.) It is also used to kill unwanted viruses and bacteria that might contaminate the vaccine during production. Most formaldehyde is removed from the vaccine before it is packaged.
• Monosodium glutamate (MSG) and 2-phenoxy-ethanol which are used as stabilizers in a few vaccines to help the vaccine remain unchanged when the vaccine is exposed to heat, light, acidity, or humidity.
• Thimerosal is a mercury-containing preservative that is added to vials of vaccine that contain more than one dose to prevent contamination and growth of potentially harmful bacteria.

For children with a prior history of allergic reactions to any of these substances in vaccines, parents should consult their child’s healthcare provider before vaccination.

Routine Mumps Immunization

Routine Mumps Immunization

What arguments can be brought against immunization for childhood diseases and specifically mumps? It is everyday experience in general practice that parents do not see childhood diseases as harmful to humans, in spite of possible complications, but as a biographical event with potential significance for their child's development. This view, based on feelings and experience, still needs scientific proof, but it would be disastrous if absence of proof were made the reason to ignore this definite opposition to the MMR immunization campaign when designing further campaigns.

For centuries, the microorganisms involved in childhood diseases such as mumps, measles and rubella showed a balanced relationship to the human population. Mass immunizations represent massive artificial intervention in those balances, with potentially unforeseeable consequences.

Epidemics are, above all, feared in populations where immunity to a particular pathogen has been lost because the disease has not occurred for some time. H. Stickl expressed concern even with regard to smallpox: "After the last case of smallpox, with the disease not recorded anywhere on earth for twice five years, which is the usual epidemic wavelength for smallpox, there was no longer any convincing reason for smallpox vaccination. Initially this was a great advantage. On careful reflection, it is evident, however, that in less than one generation an unvaccinated European population will reach the state which pertained prior to the great migrations of the 4th to 6th Century, i.e. before smallpox became endemic. People may then be expected to be completely receptive to smallpox virus infection.

Both physicians and parents would be against enforcing the higher level of compliance needed to continue the campaign. This would mean imposing government views on the Swiss health system when there is no need from the public health point of view. Constitutional lawyers doubt, however, that the limitation of basic rights in such an enforced measure would meet the requirements of suitability and reasonability.

This susceptibility to failure means that enforced measures become increasingly necessary to limit relapse epidemics. They include ensuring and maintaining immunization of the whole population, monitoring the immunity of the population, and monitoring virus circulation on borders and in quarantine situations, as well as barrier immunization procedures to limit outbreaks.

Performance and determinants of routine immunization coverage within the context of intensive polio eradication activities in Uttar Pradesh, India: Social Mobilization Network

Performance and determinants of routine immunization coverage within the context of intensive polio eradication activities in Uttar Pradesh, India: Social Mobilization Network

Background

Studies that have looked at the effect of polio eradication efforts in India on routine immunization programs have provided mixed findings. One polio eradication project, funded by US Agency for International Development (USAID) and carried out by the CORE Group Polio Project (CGPP) in the state of Uttar Pradesh of India, has included the strengthening of routine immunization systems as a core part of its polio eradication strategy. This paper explores the performance of routine immunization services in the CGPP intervention areas concurrent with intensive polio eradication activities. The paper also explores determinants of routine immunization performance such as caretaker characteristics and CGPP activities to strengthen routine immunization services.

Methods

Secondary data analysis of the latest project household immunization survey in 2011 was conducted and compare these findings to reports of past surveys in the CGPP program area and at the Uttar Pradesh state level (as measured by children’s receipt of DPT vaccinations). This is done to judge if there is any evidence that routine immunization services are being disrupted. We also model characteristics of survey respondents and respondents’ exposure to CGPP, communication activities against their children’s receipt of key vaccinations in order to identify determinants of routine immunization coverage.

Results

Routine immunization coverage has increased between the first survey (2005 for state level estimates, 2008 for the CGPP program) and the latest (2011 for both state level and CGPP areas), as measured by children’s receipt of DPT vaccination. This increase occurred concurrent with polio eradication efforts intensive enough to result in interruption of transmission. In addition, a mothers’ exposure to specific communication materials, her religion and education were associated with whether or not her children receive one or more doses of DPT.

Conclusions

A limitation of the analysis is the absence of a controlled comparison. It is possible routine immunization coverage would have increased even more in the absence of polio eradication efforts. At the same time, however, there is no evidence that routine immunization services were disrupted by polio eradication efforts. Targeted health communications are helpful in improving routine immunization performance. Strategies to address other determinants of routine immunization, such as religion and education, are also needed to maximize coverage.

IMMUNIZATION: ACHIEVEMENTS AND CHALLENGES

ACHIEVEMENTS 
Over the past decade, immunization programmes have added new and underused 
vaccines to the original six – diphtheria, tetanus, pertussis, measles, polio, and 
tuberculosis – given to young children. They include vaccines against hepatitis B, 
Haemophilus influenzae type b (Hib) disease, mumps, pneumococcal disease, 
rotavirus, rubella, and – in countries where needed – yellow fever and Japanese 
encephalitis
Immunization averts an estimated 2.5 million child deaths a year, but despite the 
successes, millions of children in developing countries – almost 20% of all children 
born every year – do not get the complete immunizations scheduled for their first 
year of life. 

BARRIERS TO INCREASE IMMUNIZATION
Reaching these children will require overcoming a number of critical barriers that have 
slowed progress. A major barrier is the underlying weakness of the health system 
in many developing countries. Another is the difficulty in delivering vaccines through 
an infrastructure and logistical support system that is often overloaded. Yet another 
is a lack of understanding about the importance of vaccines – especially among 
the poorest populations – and a failure to actively demand access to immunization 
services. The threat posed by false or unsubstantiated rumours about vaccine safety 
is also a barrier to progress, as is the projected shortfall in funding needed to reach 
the global immunization-related goals.
Efforts under way to overcome the barriers to expanded immunization include the 
use of immunization campaigns and “outreach” operations that seek out population 
groups not adequately covered by routine immunization programmes. In addition, 
special initiatives, such as the Optimize project, have been launched to help countries 
manage the growing complexity of immunization logistics (delivery and storage of 
vaccines, for example) underpinning immunization activities.

STRATEGIES FOLLOWED TO PROMOTE IMMUNIZATION
 The Reaching Every District (RED) strategy, launched in 2002, is designed to 
strengthen immunization delivery at the district level, by encouraging district-level 
immunization officials to adopt the principles of “good immunization practice”, such 

IMAGE PROMOTING IMMUNIZATION

as the identification and resolution of local problems, the organization of regular 
outreach vaccine delivery services, and the involvement of communities in ensuring 
adequate functioning of immunization services.
 Another strategy aims to integrate immunization activities with other services 
provided by the health system. Any contact that a health worker has with a child or mother at a health facility is also an opportunity to check immunization status and, 
if need be, to administer vaccines. Conversely, a mobile team offering immunization 
to a community can also distribute medicines, antimalarial bednets, and other health 
commodities or interventions.
Community participation is a key factor in raising vaccine coverage. Creating 
awareness of, and public demand for, the benefits of immunization is an essential 
component of an active immunization programme. However, it is also important to 
ensure that demand can be reliably met. 

NATIONAL IMMUNIZATION

SCHEDULE 

Every country follows an immunization schedule here is a chart of  India's immunization schedule for pregnant women, infants and children...

TYPES OF VACCINATION [VARICELLA]

VARICELLA 

[CHICKEN POX VACCINE]

About the disease...

Chickenpox (varicella) is a disease caused by a virus. Most people with chickenpox get very itchy blisters and sores all over their body.Chickenpox is spread person-to-person through the air. It is very contagious. Chickenpox can be a serious disease, especially in babies and adults. The disease can cause serious skin infections, pneumonia, brain damage, and even death. Chickenpox is especially dangerous for people whose immune systems are weak because of illness or medications.It is extremely contagious and can be spread by an infected person before they even know they're sick.Vaccination is the most effective step you can take to be protected from this serious disease.

More about the Vaccine...

The chickenpox vaccine is a shot that can protect nearly everyone who gets it from catching chickenpox. It's also called the varicella vaccine, because chickenpox is caused by the varicella-zoster virus. The vaccine is made from a live but weakened, or attenuated, virus.

Viruses that have been attenuated are less virulent than viruses that are not. Although the virus in the chickenpox vaccine is generally incapable of causing a disease, it still stimulates a response from the body's immune system. That response is what gives someone who's had a shot for chickenpox immunity or protection from the illness.

Importance of the Vaccine...

Most cases of chickenpox are relatively mild and run their course in five to 10 days. But it can be very serious, even life-threatening, in a small percentage of people.The risk of serious, life-threatening complications is greatest among infants, adults, and people with weakened immune systems. But anyone can develop serious complications and there is no way to predict who will.

There's another reason for getting a shot for chickenpox. The illness is highly contagious and can be spread by direct contact or through the air by sneezing or coughing. Also, someone can get it by coming in contact with fluid from chickenpox blisters. For that reason, children with chickenpox need to be kept out of school or day care for about a week or more until all blisters have dried and crusted over. The illness causes an itchy rash that usually forms between 200 and 500 blisters over the entire body, headaches, coughing, and fussiness. So even if the illness is mild, it still means five to 10 days of being uncomfortable.

Vaccine Schedule...

All children should get 2 doses of chickenpox vaccine starting at age 1. Some teens and adults may also need this vaccine if they didn't get 2 doses of the vaccine or chickenpox disease when they were younger.