Can too many vaccines overwhelm an infant"s immune

[nicole]

Q. Can too many vaccines overwhelm an infant"s
immune system?
A. No.

Compared to the immunological challenges that infants
handle every day, the challenge from the immunological components
in vaccines is minuscule.

Babies begin dealing with immunological challenges at birth. The
mother"s womb is a sterile environment, free from viruses, bacteria,
parasites and fungi. But after babies pass through the birth canal
and enter the world, they are immediately colonized with trillions
of bacteria, which means that they carry the bacteria on their bodies
but aren"t infected by them. These bacteria live on the skin, nose,
throat and intestines. To make sure that colonizing bacteria don"t
invade the bloodstream and cause harm, babies constantly make
antibodies against them.

Colonizing bacteria aren't the only issue. Because the food that we
eat and the dust that we breathe contain bacteria, immunological
challenges from the environment are unending. Viruses are also a
problem. Children in the first few years of life are constantly
exposed to a variety of different viruses that cause runny noses,
cough, congestion, fever, or diarrhea.

Given that infants are colonized with trillions of bacteria, that each
bacterium contains between 2,000 and 6,000 immunological
components and that infants are infected with numerous viruses,
the challenge from the 150 immunological components in vaccines
is minuscule compared to what infants manage every day.

By UnbiasedScientist

[nicole]

Addressing Parents’ Concerns: Do Multiple Vaccines Overwhelm or Weaken the Infant’s Immune System?

Source:PEDIATRICS Vol. 109 No. 1

INTRODUCTION

One hundred years ago, children received 1 vaccine (the smallpox vaccine). Forty years ago, children received 5 vaccines routinely (diphtheria, pertussis, tetanus, polio, and smallpox vaccines) and as many as 8 shots by 2 years of age. Today, children receive 11 vaccines routinely and as many as 20 shots by 2 years of age (Table 1). The increased number of vaccines given to children and the increased percentage of children receiving vaccines have resulted in a dramatic decrease in the number of vaccine-preventable diseases.

Most young parents today have never seen many of the diseases that vaccines prevent. As a possible consequence of these trends, recent national surveys found that 23% of parents questioned the number of shots recommended for their children,1 and 25% were concerned that vaccines might weaken the immune system.

Because most parents receive information and recommendations about vaccines from their doctors,² and because these recommendations carry substantial weight with parents,^3,4 providers must be knowledgeable when addressing parents’ concerns. This article will provide health care professionals with information about the effect of vaccines on the infant’s immune system and the capacity of the immune system to respond safely to multiple vaccines ¹.

A BRIEF SUMMARY OF NEONATAL AND INFANT IMMUNE RESPONSES

The Neonatal Immune System

Neonates develop the capacity to respond to foreign antigens before they are born. B and T cells are present by 14 weeks’ gestation and express an enormous array of antigen-specific receptors.5 Although the fetal immune system has the potential to respond to large numbers of foreign antigens, few foreign antigens are present in utero, and cells of the immune system are, therefore, primarily "naïve" at birth.

Passively Acquired Immunity

The neonate is, in part, protected against disease by maternal immunoglobulins (Ig). Maternal IgG is transported across the placenta before birth and maternal secretory IgA is present in breast milk and colostrum. These passively acquired antibodies provide protection against pathogens to which the mother was immune. However, protection provided by passively transferred antibodies is short-lived. Passively acquired maternal IgG declines during the first few months of life,6 and most infants are not breastfed beyond several months of age.7 More importantly, maternal antibodies offer limited immunologic protection when compared with protection afforded by an infant’s active immune response.

Active Immunity

Neonates are capable of generating both humoral and cellular immune responses to pathogens at the time of birth.^8,9 Active immunity in the newborn includes the full range of B-cell responses including the production of IgM, IgG, and secretory and monomeric IgA, as well as the development of helper T-cell (Th) and cytotoxic T-cell responses.^8,9 In addition, neonates can produce specific Th-cell subsets, including Th1-type cells that participate in cell-mediated immune responses and Th2-type cells that are primarily involved in promoting B-cell responses.^8,9

The development of active humoral and cellular immune responses in the newborn is necessary to meet the tremendous number of environmental challenges encountered from the moment of birth. When children are born, they emerge from the relatively sterile environment of the uterus into a world teeming with bacteria and other microorganisms. Beginning with the birth process, the newborn is exposed to microbes from the mother’s cervix and birth canal, then the surrounding environment. Within a matter of hours, the gastrointestinal tract of the newborn, initially relatively free of microbes, is heavily colonized with bacteria.¹⁰ The most common of these colonizing bacteria include facultative anaerobic bacteria, such as Escherichia coli and streptococci, and strict anaerobic bacteria, such as Bacteroides and Clostridium.¹⁰ Specific secretory IgA responses directed against these potentially harmful bacteria are produced by the neonate’s intestinal lymphocytes within the first week of life.¹¹

Functional Differences Between Infant and Adult Immune Responses

Although infants can generate all functional T-cells (ie, Th1, Th2, and cytotoxic T-cells),^8,9 infant B-cell responses are deficient when compared with older children and adults. Infants respond well to antigens (such as proteins) that require T-cell help for development. However, until about 2 years of age, the B-cell response to T-cell-independent antigens (such as polysaccharides) is considerably less than that found in adults.¹² For this reason, infants are uniquely susceptible to bacteria that are coated with polysaccharides (such as Haemophilus influenzae type b [Hib] and Streptococcus pneumoniae).

FURTHER INFORMATION:

IMMUNE RESPONSE TO VACCINES BY NEONATES

IMMUNE RESPONSE TO VACCINES BY INFANTS

IMMUNE RESPONSE TO VACCINES BY CHILDREN WITH IMMUNODEFICIENCIES

IMMUNE RESPONSE TO VACCINES BY CHILDREN WITH MILD, MODERATE, OR SEVERE ILLNESSES

DO VACCINES "OVERWHELM" THE IMMUNE SYSTEM?

DO VACCINES "WEAKEN" THE IMMUNE SYSTEM?

SUMMARY

Current studies do not support the hypothesis that multiple vaccines overwhelm, weaken, or "use up" the immune system. On the contrary, young infants have an enormous capacity to respond to multiple vaccines, as well as to the many other challenges present in the environment. By providing protection against a number of bacterial and viral pathogens, vaccines prevent the "weakening" of the immune system and consequent secondary bacterial infections occasionally caused by natural infection.