Immunization Issues
Do Multiple Vaccines Overwhelm the Immune System?
Updated: 06/05/2008
In the early 1940s only one vaccine was given routinely: smallpox. Later that decade, the
diphtheria, pertussis, and tetanus vaccine began to be given routinely. Now, by the time a
newborn is 12 years of age, she will have received 30-35 doses of vaccines to protect her against
34 diseases.
Looking at the number of shots given at each pediatric visit, many parents wonder whether a
baby’s immune system can withstand so many immunizations—almost half of the parents in a
survey expressed this concern as a reason for not vaccinating their children.(1)
Can a children’s immune system handle all those vaccines? (2-5) The answer seems to be yes it
can.
- Even though an infant's immune system cannot respond to all the different types of foreign
materials (called antigens) in the same way an adult can, infants do have an amazing ability to
respond to an extremely large number and numerous types of antigens. The number a child can
respond to is many more than the number of vaccine antigens given in the early years of life.
- Because of newer ways of making vaccines, the number of antigens (substances that induce
immune responses) in vaccines has actually decreased since 1980. For example, the old whole
cell pertussis vaccine contained about 3,000 antigens, whereas the newer acellular pertussis
vaccine contains only a few. So while we give more shots, the number of antigens that the
immune system must respond to is actually many fewer than before. (2)
- Before each of these vaccines can be licensed in the United States, they have to be shown to
effectively stimulate the immune system—for all the vaccine components—and to be effective
along with all the components of vaccines that would usually be given at the same time.
- A number of studies have observed no increased risk of other types of infections after vaccines
and some have even shown fewer infections in immunized children.(4, 6 , 7) One study could
find no effect on hospital admissions for other types of infections and how many and which
vaccines a child had received—among all the children born in Denmark born from 1990 through
2001. (6)
The fact is that vaccines strengthen, not weaken, the immune system. This is true even for
newborn infants. On the other hand, a natural infection clearly can weaken a child’s immune
system. For example, a previously healthy child with chickenpox (varicella) may become
infected with dangerous bacteria, resulting in an infection severe enough to require
hospitalization or even cause death. Similarly, a child with measles infection is more likely to
develop middle ear infections.
Infants and children are bombarded with germs every day in the air they breathe and the food
they eat, but their immune systems are able to handle these exposures. The vaccines that are
recommended for all children use only a small portion of the immune system’s “memory.”
Scientists estimated that based on the immune system’s capacity to respond, a child could
theoretically get 10,000 vaccines in one day and still not “use up” his or her immune ability to
respond. (2)
This Immunization Issues essay is an excerpt from the book Do Vaccines Cause That?! A Guide
for Evaluating Vaccine Safety Concerns written by NNii authors Martin G. Myers and Diego
Pineda.
References
1. Daniel A. Salmon, PhD, MPH; Lawrence H. Moulton, PhD; Saad B. Omer, MBBS, MPH; M.
Patricia deHart, ScD; Shannon Stokley, MPH; Neal A. Halsey, MD. Factors Associated With
Refusal of Childhood Vaccines Among Parents of School-aged Children: A Case-Control Study.
Arch Pediatr Adolesc Med. 2005;159:470-476.
2. Offit PA, Quarles J, Gerber MA, et al. 2002. Addressing parents concerns: do multiple
vaccines overwhelm the infant’s immune system. Pediatrics. 109(1): 124-9.
3. Hilton S, Petticrew M, Hunt K. 2006. ‘Combined vaccines are like a sudden onslaught to the
body’s immune system’: parental concerns about vaccine ‘overload’ and ‘immune vulnerability’.
Vaccine 24: 4321-7.
4. Gregson AL, Edelman R. 2003. Does antigenic overload exist? The role of multiple
immunizations in infants. Immunol Allergy Clin N Am. 23: 649-664.
5. Gellin BG, Maibach EW, Marcuse EK, et al. 2000. Do parents understand immunizations? A
national telephone survey. Pediatrics 106(5): 1097-1102.
6. Hviid A, Wohlfahrt J, Stellfeld m, et al. 2005. Childhood vaccination and nontargetted
infectious disease hospitalization. JAMA 294(6): 699-705.
7. Institute of Medicine Immunization Safety Review Committee. Multiple immunizations and
immune dysfunction. National Academy Press, Washington, DC, 2002.