An unwavering belief in the triumph of vaccines over infectious diseases is common among people raised in the era when scourges like polio and smallpox were conquered, and when immunization against childhood diseases was part of growing up.

Today, however, diseases once thought to be under control are re-emerging. For the past couple of years, a mumps epidemic has been developing in the United Kingdom.¹ In 2005, more than 56,000 cases were reported in England and Wales alone. Most of the affected people were born between 1983 and 1986 and had not been vaccinated against mumps; vaccinations have been offered routinely only since 1988. Furthermore, only 2.4 percent of eligible people who received a second inoculation, a program introduced in 1995, developed mumps during this recent outbreak.

As of early May, more than 1,500 people had been diagnosed with mumps in Iowa. Additional cases also had been reported in adjoining states. This is a significant increase compared with the usual 250 to 300 annual cases across the United States. Some of the people affected by the most recent outbreak have been vaccinated, yet they developed acute cases of the disease.

The mumps vaccine was introduced in the United States in 1967 and has been administered routinely since 1977. The recommendation for two inoculations, which would increase the likelihood of full immunity, was instituted only in the 1990s. Not surprisingly, therefore, many of these new cases are found in people aged 18 to 25 years—people who received only one inoculation and who were not exposed to mumps during childhood.

It has been postulated that two infected people traveling on several domestic commercial flights during late March and early April facilitated the spread of this outbreak.² This is the first time that a possible mumps transmission during air travel has been reported.

Mumps outbreaks in the United Kingdom and the United States illustrate several important points:

– aerosolized infections can be spread by air travel;

– even people who have received vaccinations do not always have sufficient immunity to ward off an infection;

– a second inoculation may provide enhanced protection;

– natural immunity to certain infections, such as mumps, usually confers immunity;

– natural immunity to disease with a low mortality rate will decline within the population after routine immunization programs are implemented;

– identification and subsequent isolation of infectious people would limit the spread of an outbreak.

In the case of mumps, salivary diagnostics are available to identify both mumps-specific immunoglobulin M antibodies and the virus itself, which is present days before the onset of symptoms. It begs to be asked whether the involvement of oral health care professionals could afford earlier identification of infected people in areas of an outbreak.

Perhaps insights can be gained from epidemics—such as the recent mumps outbreaks—that could be applied in the event of a pandemic. The continuous and rapid spread of the highly pathogenic avian influenza virus H5N1 among migratory and domestic birds underscores the need to develop an effective vaccine for humans.

To date, more than 200 people reportedly have been infected with H5N1, and more than 100 of those infected have died. Although only a handful of these infections are suspected to have occurred through human-to-human transmission, a genetic drift of this virus—an exchange, or reassortment of genetic material between avian and human influenza viruses, or direct transmission of strains from an animal source to humans—could create a new virus with the potential for effective human-to-human transmission.

Such an occurrence could be the start of a devastating pandemic associated with an overwhelming morbidity and mortality. Some experts have predicted that without effective treatment and prophylactic measures, the human death toll could reach 1.9 million in the United States and 200 million worldwide.

The development of a vaccine against H5N1 is a race against time and, at the same time, a gamble that the vaccine actually will target the specific agent responsible for this impending pandemic. Many obstacles stand in the way of developing such a vaccine. One technique for producing an avian influenza vaccine is reverse genetics. This process involves retaining non-pathogenic surface antigens from an original virus to produce a nonpathogenic replica of the pathogenic source virus. Currently, the process takes two to three months. A recent study of the safety and efficacy of such a formed vaccine showed great promise. It was associated with few minor side effects and in high doses produced neutralizing hemagglutinin-specific antibodies in more than 50 percent of healthy adults aged 18 to 64 years.³

It is not known at what concentration these antibodies would confer maximum immunity, but it is clear that a lower antigen concentration, needed to produce a vaccine, would optimize mass production. An aluminum phosphate adjuvant whole-virion H5N1 vaccine has yielded a significant reduction of antigen content while still maintaining immunogenicity.⁴ This approach has, in a small study, produced successful immune responses in up to 90 percent of recipients. Encouraging results also have been achieved with other adjuvants, such as MF59, which can boost the immune system similarly.⁵

Although great progress is being made in the efforts to produce an effective avian flu vaccine, several questions remain unanswered. If the vaccine that has been developed targets a specific strain of H5N1 and the pandemic is caused by a different strain, or even another type of avian influenza virus, will the existing vaccine still provide some level of protection? Should a vaccine that is only partially protective still be distributed? Will one inoculation be enough? Will there be enough information to assess the safety among all categories of people—the very young, the very old, the immunocompromised? Who should be the primary recipients in case of an outbreak if there is not enough vaccine for the entire population? Could the vaccine be used as a "therapeutic" vaccine to reduce the signs and symptoms in already-infected people? If given to infected people, could it reduce contagion?

These are questions that may be posed to all health care providers, including dentists. To minimize any potential panic associated with an influenza pandemic, it is essential that all oral health care professionals familiarize themselves with the necessary information regarding transmission, contagion, treatment and prophylaxis. Such an effort will greatly reduce misconceptions, myths and rumors, and potentially will save lives.

Oral health care professionals, when given the opportunity, can have a major impact on containing infectious outbreaks in their communities, ranging from collecting samples for identification of infected people to being a resource of facts for patients and the community at large. For the safety and benefit of our patients, we need to take a proactive role.