The growing use of vaccines by Americans, including Mainers, as well as by people all over the world, marks a giant step toward better health for all mankind. But further progress is now threatened and, unless we take action, may actually be reversed.

First, some facts about the dramatic contributions of vaccines. Since World War II, according to a 2005 report by David Bloom of Harvard and two colleagues, vaccination campaigns have scored these successes:

? Smallpox killed 2 million people a year until the late 1960s, but by 1979, after a worldwide immunization campaign, it was wiped out.

? Deaths from measles dropped from 6 million a year in 1974 to less than 500,000 in 2004.

? Immunization campaigns have eliminated or drastically reduced illness and death from neonatal tetanus, polio, whooping cough and diphtheria.

? Today, 26 diseases are vaccine-preventable.

Mainers, along with the rest of the world, have benefited from vaccines. The Margaret Chase Smith Center for Public Policy reports no deaths in Maine from smallpox since 1929, from diphtheria since 1964, from whooping cough since 1967 and from tetanus since 1970. And Maine’s immunization efforts are continuing. Among children entering Maine schools in 2003, a huge 95 percent received DTP, the vaccine for diphtheria, tetanus and pertussis (whooping cough).

Vaccination is so effective largely because it offers widespread benefit: it not only protects the person receiving the vaccine but also the friends and relatives who could have caught the disease. You and I are protected by the vaccination of family members, of people from neighboring towns and of persons from other countries who land at Bangor International Airport or drive here from Boston.

History shows that Mainers are vulnerable to diseases originating overseas, like the influenza epidemic of 1918, which killed 5,000 Mainers and the AIDS virus, which presently infects 1,500 and has killed more than 500. Bird flu, another threat originating elsewhere, has not yet killed Americans, but it has spread rapidly from China to other parts of Asia, Europe and Africa. Epidemiologists predict that it will eventually reach the United States. The development of effective vaccines is at the heart of both the effort to avoid a bird-flu pandemic and to fight the spread of AIDS.

Clearly, Mainers benefit immensely from immunization campaigns everywhere. As worldwide vaccination rates for six major diseases have risen from less than 5 percent in 1974 to more than 70 percent today, our vulnerability to disease has been reduced.

But the picture is not all upbeat. Worldwide, 2 million people still die each year from vaccine-preventable diseases. Furthermore, continued progress is being threatened by actions of both the recipient populations and the vaccine producers.

In several countries, the percentage of children receiving the DTP vaccine has declined by half since 1990. And the number of major Western drug companies making vaccines has fallen from 26 in 1967 to five today.

Three problems mainly account for this situation. First, anti-vaccine movements have arisen in several countries, including the United States and Nigeria. Some people in the United States assert, without scientific foundation, that some vaccines cause autism and brain damage, while others exaggerate the small risks of side effects. In northern Nigeria, Islamic clerics maintained that the polio vaccine is contaminated with anti-fertility hormones and the AIDS virus. As a result, vaccination was suspended in several Nigerian states; the incidence of polio rose and the disease spread to at least four other African countries.

Second, falling research budgets in Western countries have inhibited the development of new vaccines. In the United States, the growth of managed care has tightened medical care markets, causing hospital-based research funding to plummet.

Third, and most important, there are few incentives for drug companies to produce vaccines or to develop new vaccines for diseases common in poor countries, where few people can afford to pay for vaccines. The developing-world vaccine market is only 10 or 15 percent of the world total.

So, what can we do?

We can ensure that our own children are vaccinated, to lower the risk that dreaded diseases will return.

We can support the international agencies and nonprofit organizations that promote vaccination. The Global Alliance for Vaccines and Immunization (GAVI), which brings together United Nations agencies, governments, private foundations and drug companies, is promoting increased use of vaccines for the common childhood diseases and for other diseases such as yellow fever.

The Bill and Melinda Gates Foundation is giving $1.5 billion to GAVI, and it has also made grants totaling $290 million to accelerate the pace of HIV vaccine development.

And, last, we can encourage the U.S. government to raise its current pledge of $2.5 billion to the international program that purchases huge quantities of vaccines for use in developing countries, thereby providing an incentive for drug companies to resume vaccine production.

Together, these efforts could save millions of lives around the world, and your child’s or grandchild’s life could be one of them.

Edwin Dean, a seasonal resident of Vinalhaven, writes monthly about economic issues.