Infant-measles wave traced to 1960s vaccinations.

A generation ago, doctors routinely began vaccinating every child against measles. No one worried much what would happen when they grew up and had babies of their own.

In hindsight, perhaps they should have: these new mothers fail to pass on the strong resistance to measles at birth that an eternity of women before them have done. The result is a new problem--measles in the very young.

This unforeseen by-product of a well-meaning public health campaign has become apparent over the past two or three years, as larger numbers of vaccinated women have reached their childbearing years. Because the mothers got vaccinated, their babies are unusually susceptible to measles in their first year of life, when it is a potentially life-threatening disease.

Now, more than one-quarter of all U.S. measles victims are under a year old, an age when this disease was once almost unheard of.

Experts caution that this does not mean that girls should not be vaccinated. In fact, the disease is overwhelmingly less common that it was until the 1960s, when virtually everyone caught it. They contend measles would not be a problem for newborns, either, if more toddlers got the vaccine.

Nature once took care of this. Before the vaccine era, when measles was an unavoidable rite of childhood, everyone who recovered carried high levels of measles antibodies the rest of their lives. This kept the virus from coming back. When women give birth, they pass on this protection to help babies ward off measles until their own immune systems mature.

The amount of antibodies a baby gets at birth depends on how much his mother carries. If the mother has a lot. so will the child.

Like a natural measles infection, the vaccine triggers production of measles antibodies. However, the amounts are lower. So vaccinated mothers have fewer antibodies to pass to their babies than do those who had the disease.

This means their babies become prone to catching measles at an earlier age. The children of naturally infected mothers arc often protected from measles until around age 15 months or so. But vaccinated mothers' babies may be at risk at age 6 months or sooner.

CDC figures show how this has changed the face of measles. In 1976, just 3 percent of all cases occurred in children under age 1. Typically, their mothers were born in the 1950s, well before the measles vaccine became routinely available a decade later.

In the 1980s, as teenagers who were vaccinated as children began to have babies, those numbers started to change, In 1985, almost 8 percent of measles cases were in infants under age 1. By 1991, it had climbed to 19 percent, And so far this year, it's been running at 28 percent. -- From the Ann Arbor News, 11/22/92