Vaccines and “immune system overload”

In 2002, Dr. Paul Offit and several others published a peer-reviewed paper:  “Addressing Parents’ Concerns: Do Multiple Vaccines Overwhelm or Weaken the Infant’s Immune System?”

One interesting point was the number of antigens that children are exposed to. I’ll just mention a couple of the conclusions:

• First, theoretically a baby’s  immune system can handle at least 10,000 antigens at one time, just based on the number of circulating immune cells.
• Second, children’s vaccinations expose them to far fewer foreign proteins now than in 1980–about 4% of the number (or 3.8% of the number given in 1960).

Antigen exposure has dropped 96% since 1980

You can get a full-sized copy of this graph on flickr. feel free to spread it around.

Children are Exposed to Fewer Antigens in Vaccines Today Than in the Past

Parents who are worried about the increasing number of recommended vaccines may take comfort in knowing that children are exposed to fewer antigens (proteins and polysaccharides) in vaccines today than in the past.

Table 2 summarizes the number of proteins and polysaccharides contained in routinely recommended vaccines administered over the past 100 years. Although we now give children more vaccines, the actual number of antigens they receive has declined. Whereas previously 1 vaccine, smallpox, contained about 200 proteins, now the 11 routinely recommended vaccines contain fewer than 130 proteins in total.

Two factors account for this decline: first, the worldwide eradication of smallpox obviated the need for that vaccine, and second, advances in protein chemistry have resulted in vaccines containing fewer antigens (e.g., replacement of whole-cell with acellular pertussis vaccine).

The paper covers several other interesting points.

Abstract: Recent surveys found that an increasing number of parents are concerned that infants receive too many vaccines. Implicit in this concern is that the infant’s immune system is inadequately developed to handle vaccines safely or that multiple vaccines may overwhelm the immune system. In this review, we will examine the following:

1) the ontogeny of the active immune response and the ability of neonates and young infants to respond to vaccines;

2) the theoretic capacity of an infant’s immune system;

3) data that demonstrate that mild or moderate illness does not interfere with an infant’s ability to generate protective immune responses to vaccines;

4) how infants respond to vaccines given in combination compared with the same vaccines given separately;

5) data showing that vaccinated children are not more likely to develop infections with other pathogens than unvaccinated children; and

6) the fact that infants actually encounter fewer antigens in vaccines today than they did 40 or 100 years ago.