Factors Leading To Measles Vaccine Failure Rate

What Is Measles?

Measles is a viral infection known to induce a distinctive rash characterized by red, patchy patterns. Typically, it emerges initially on the face and areas behind the ears, subsequently progressing downward to the chest and back and eventually reaching the feet. Measles symptoms manifest approximately 10 to 14 days following exposure to the virus. Common signs and symptoms of measles include:

• Fever.

• Dry cough.

• Runny nose.

• Sore throat.

• Tiny white spots with bluish-white centers are found inside the mouth on the inner lining of the cheek (Koplik's spots).

• Inflamed eyes (conjunctivitis).

• Skin rash: Large, flat blotches that often merge together.

What Is Measles Vaccine?

The prevention of measles is achievable through the administration of the MMR (measles, mumps, and rubella) vaccine. It provides protection against measles, mumps, and rubella. The recommended schedule for the MMR vaccine for individuals not traveling:

Children:

• First Dose: Administered at the age of 12-15 months.

• Second Dose: Given between the ages of 4-6 years.

Teenagers and Adults With No Evidence of Immunity:

First Dose: It is advised to receive the MMR vaccine as soon as possible. The first dose provides a good level of protection, and the second dose is necessary to ensure long-term immunity and maximize effectiveness. Following the recommended vaccination schedule helps to safeguard against the risk of contracting measles, mumps, and rubella.

The promotion and maintenance of widespread immunity play a crucial role in preventing the resurgence of measles. The introduction of the measles vaccine has led to the virtual elimination of measles. This achievement is attributed to the concept of herd immunity. However, there has been a recent weakening of herd immunity, possibly due to a decline in vaccination rates.

To prevent a resurgence of measles, it is essential to maintain steady and consistent vaccination rates. When vaccination rates start to decline, measles has the opportunity to resurface and spread within communities. Therefore, ensuring that vaccination rates remain high is crucial in keeping measles under control and minimizing its impact on public health.

What Are the Stages of Measles Infection?

• Infection and Incubation: During the first 10 to 14 days after contracting the virus, there are no visible signs or symptoms of measles.

• Nonspecific Signs and Symptoms: Measles typically begins with a mild to moderate fever, persistent cough, runny nose, inflamed eyes, and a sore throat. This phase, characterized by relatively mild illness, lasts for about two to three days.

• Acute Illness and Rash: It can present as a rash with small red spots, some of which may be slightly raised. These spots and bumps cluster together, giving the skin a reddish, splotchy appearance. The rash initially appears on the face and then spreads downwards.

Over the next few days, the rash extends to the arms, chest, back, thighs, lower legs, and feet. Simultaneously, the fever intensifies, often reaching high temperatures of 104 to 105.8 F (40 to 41 C).

• Recovery: The infection that presents as a rash typically persists for about seven days. It fades away gradually, starting from the face, and lasts to disappear from the thighs and feet. As other symptoms subside, coughing and temporary darkening or peeling of the skin where the rash was located may persist for approximately ten days.

What Are the Factors Leading To Measles Vaccine Failure Rate?

Two rare types of vaccine failure can render individuals susceptible to infection even after vaccination:

Primary Vaccine Failure: Approximately 1 out of every 100 vaccinated individuals may not develop the expected protective antibody response despite receiving two doses of the measles vaccine. This condition is referred to as primary vaccine failure. Initially, measles vaccination involved a single dose when it was introduced in 1963. However, to address primary vaccine failure, a second dose was added to the vaccination schedule in 1989, aimed at reducing the number of individuals who experience this type of vaccine failure.

Secondary Vaccine Failure: Secondary vaccine failure occurs when the antibody response to the vaccine diminishes over time. This type of failure appears to be even rarer than primary vaccine failure, and for the majority of individuals, measles vaccination is believed to provide lifelong protection.

Insufficient immunization remains a significant factor contributing to the persistence of measles in the United States. In 1971, there were more than 70,000 reported cases of measles, with a majority occurring in previously vaccinated children. Several reasons have been proposed to explain these vaccine failures:

• Improper Storage or Handling of the Vaccine: If the live virus in the vaccine is not stored or handled correctly, it can become inactive, rendering it ineffective in providing immunity.

• Inhibition of Active Response to the Virus: Maternally transmitted or artificially administered passive antibodies can interfere with the body's ability to mount an active immune response to the live virus in the vaccine.

• Seroconversion Failure Rate: Approximately 5 % of individuals may fail to develop the desired immune response after receiving the vaccine.

• Modified Illness and Secondary Antibody Response: Some children may experience a modified form of the illness after vaccination, resulting in a secondary type of antibody response. Assuming a 10 % failure rate in a given population, it is estimated that 7 % of those vaccinated will not respond adequately, while 3 % may initially respond but subsequently lose their immunity.

A study conducted at the Oguntolu Street Clinic in Lagos between October 1982 and February 1983 aimed to investigate the reasons behind the high failure rate of the measles vaccine. The study identified three possible factors contributing to the vaccine's failure:

• Circulating Maternal Antibodies: One reason for the vaccine's failure was the presence of maternal antibodies circulating in the infants' systems. This accounted for 67.7% of the cases, particularly among children aged 6-7 months. However, it was observed that high antibody levels before vaccination did not necessarily correlate with vaccine failure.

• Administration of Non-viable Vaccines: The study concluded that the administration of non-viable vaccines is not a factor contributing to the failure. All vials of the measles vaccine used during the study were found to be potent at the time of administration.

• Misdiagnosis: In 32.3% of cases, the failure of the measles vaccine was attributed to an incorrect diagnosis. This suggests that some cases were misdiagnosed as vaccine failures when other factors were responsible.

The findings indicate that the failure to seroconvert (developing the desired immune response) was the primary cause of vaccine failure, particularly in infants aged six to seven months.

Conclusion

It is recommended that all children vaccinated before the age of 1 year receive a revaccination. Additionally, an additional 5 to 15 % of children may require a booster dose. Ensuring proper immunization practices, addressing vaccine storage and handling, and improving vaccination strategies are vital in reducing the incidence of measles and achieving higher levels of population immunity.