STDs against which vaccine prophylaxis is given

One of the most effective methods of preventing the spread of STDs is preventive immunization.

Currently, licensed vaccines are available for hepatitis A and hepatitis B. Vaccines against several STDs, including HIV and herpes, are in development or clinical trials. As more effective vaccines become available, immunization will become one of the most common methods of preventing STDs.

There are 5 different viruses (A-E) that cause almost all human viral hepatitis. Serologic testing is necessary to ensure the correct diagnosis. For example, a health care provider may suspect that jaundice in an intravenous drug user is due to hepatitis B, whereas hepatitis A outbreaks are common among intravenous drug users. Formulating the correct diagnosis is the cornerstone of providing appropriate preventive measures. To ensure reliable reporting of viral hepatitis cases and adequate prophylaxis in individuals who have had close household or sexual contact with a patient with hepatitis, it is necessary to establish the etiology of viral hepatitis in each case using appropriate serologic testing.

Hepatitis A

Hepatitis A is caused by the hepatitis A virus (HAV). HAV multiplies in the liver and is excreted in feces. The highest concentration of the virus in feces is detected in the period from two weeks before and during the first week of the onset of clinical signs of the disease. During this period, the virus is also detected in the blood serum and saliva, but in lower concentrations than in feces. The most common route of transmission of HAV is fecal-oral: from person to person during close household or sexual contact, or through contaminated food or water. Transmission of the infection to sexual partners can occur through oral-anal contact, which can occur between heterosexual and same-sex sexual partners. Since viremia is observed during the acute period of infection, HAV can be transmitted through blood, but such cases are rare. Although HAV is present in small amounts in the saliva of an infected person, saliva does not play a role in the transmission of the infection.

Up to 20% of patients with acute hepatitis A require hospitalization, and 0.1% develop progressive liver failure. The overall mortality rate from acute hepatitis A is 0.3%, but it is higher (1.8%) in people over 49 years of age. HAV infection is not associated with chronic liver disease.

In 1995, there were 31,582 persons with hepatitis A in the United States. The most common modes of transmission included close household or sexual contact with a person infected with hepatitis A, caregiving or work settings, recent international travel, homosexual contact, injection drug use, and foodborne or waterborne outbreaks. Many persons with hepatitis A have no identified risk factors and may have acquired their infection from other asymptomatic infected persons. The prevalence of hepatitis A in the general population is 33% (CDC, unpublished data).

Outbreaks of hepatitis A among homosexual men have been reported in urban areas both in the United States and abroad. The incidence of hepatitis A in homosexual men is significantly higher than in heterosexual men (30% compared with 12% in one study). A case-control study in New York City found that homosexual men with acute viral hepatitis had more unknown sexual partners and were likely to engage in more group sex than controls; there was an association between the frequency of oral-anal contact (oral role) and digital-rectal contact (digital role) and the incidence of the disease.

Treatment

Because hepatitis A is not a chronic infection, treatment is generally supportive. Hospitalization may be necessary for patients who are dehydrated due to nausea and vomiting or rapidly developing liver failure. Medications that can cause liver damage or that are metabolized by the liver should be used with caution.

Prevention

General measures to prevent hepatitis A, such as good personal hygiene, do not affect the transmission of the virus from person to person through sexual contact. To control outbreaks of hepatitis A among heterosexual and bisexual men, health education should emphasize the modes of transmission of HAV and measures that can be taken to reduce the risk of transmission of STIs, including enteric pathogens such as HAV. However, the most effective way to prevent hepatitis A is immunization.

There are two types of drugs available for the prevention of hepatitis A, immunoglobulin (IG) and a vaccine. IG is a solution containing antibodies obtained from human plasma by precipitation with the addition of ethanol, which also inactivates HSV and HIV. When administered intramuscularly before infection or within two weeks of infection, IG is able to prevent hepatitis A in more than 85% of cases. IG is recommended for various situations of possible infection, including use in individuals who have had close sexual or household contact with patients with hepatitis A. The duration of the protective effect is relatively short (3-6 months) and depends on the dose.

Inactivated hepatitis A vaccines have been used in the United States since 1995. These vaccines are safe, highly immunogenic, and effective, and appear to provide longer-lasting protection against hepatitis A than IgV. Immunogenicity studies show that the first dose of the vaccine provides immunity in 99% to 100% of individuals; the second dose provides longer-lasting protection. Studies show that the preventive efficacy of inactivated hepatitis A vaccines is 94% to 100%.

Vaccination before infection

Preventive vaccination is indicated for the following risk groups who may be visitors to institutions where STD treatment is carried out.

• Men who have sex with men. Sexually active men who have sex with men (both adolescents and adults) should be vaccinated.
• Drug users. Vaccination is recommended for drug users who inject or non-inject drugs if local epidemiological data indicate a past or ongoing outbreak of the disease among individuals with such risk behavior.

Vaccination after infection

Persons who have recently been infected with HAV (i.e., close sexual or household contact with a person with hepatitis A) and who have not previously been vaccinated should be given a single dose of IG IM (0.02 ml/kg) as soon as possible, but no later than 2 weeks after suspected exposure. Persons who have received at least one dose of hepatitis A vaccine at least 1 month before suspected exposure to a patient with hepatitis A do not need IG. IG should be given as soon as possible, but is not effective if given more than 2 weeks after exposure.

Hepatitis B

Hepatitis B (HB) is a common STD. Sexual transmission has occurred in 30-60% of the 240,000 new cases of hepatitis B that have occurred annually in the United States over the past 10 years. Among infected adults, chronic infection develops in 1-6% of cases. These individuals can transmit the virus to others and are at risk for fatal complications of the disease. In the United States, HBV is estimated to cause 6,000 deaths from cirrhosis and hepatocellular carcinoma each year.

The risk of perinatal transmission of hepatitis B to newborns from infected mothers is 10-85%, depending on the presence of hepatitis B virus (HBV) e antigen in the mother. Infected newborns become carriers of viral hepatitis B and are at risk of developing chronic liver disease. Even in the absence of infection during the perinatal period, children of infected mothers remain at high risk of infection through contact and household contact during the first 5 years of life.

Treatment

There is no specific treatment for viral hepatitis B. Detoxification and symptomatic treatment are usually used. Over the past four years, many antiviral drugs have been studied for the treatment of chronic hepatitis B. Alpha-2b interferon is effective in 40% of cases of chronic hepatitis B, mainly in individuals who became infected as adults. Antiretroviral drugs (eg, lamivudine) have been shown to be effective in hepatitis B and research in this area is ongoing. The goal of antiretroviral therapy is to stop the replication of viral hepatitis B and the criterion for the effectiveness of treatment can be considered the normalization of liver function tests, improvement of liver histological examination parameters and obtaining a negative serological reaction to HBsAg, instead of the previously determined positive reaction. Observations of patients treated with alpha interferon have shown that remission of chronic hepatitis caused by the use of this drug is of long duration. The effectiveness of interferon treatment is associated with low levels of hepatitis B viral DNA before treatment, high levels of ALAT before treatment, short duration of infection, infection in adulthood, positive dynamics of histological examination and female gender.

Prevention

Although methods used to prevent other STDs should also prevent HBV infection, hepatitis B immunization is the most effective method for preventing this infection. The epidemiology of hepatitis B in the United States indicates that age-specific interventions are necessary to achieve broad population immunization and effectively prevent transmission of HBV and HBV-related chronic liver disease. Vaccination of individuals with a history of STDs is part of a comprehensive strategy to eliminate hepatitis B in the United States. This strategy also includes: prevention of prenatal infection through routine screening of all pregnant women; routine vaccination of all newborns; vaccination of older children at high risk of infection (eg, Alaskans, Pacific Islanders, and first-generation immigrants from countries with high or intermediate endemicity of HBV); vaccination of 11- to 12-year-old children who have not been previously vaccinated against hepatitis B, and vaccination of adolescents and adults at high risk.

Vaccination before infection

With the introduction of routine hepatitis B vaccination in newborns and the introduction of widespread vaccination programs for adolescents, vaccination of high-risk adults has become a priority for hepatitis B prevention in the United States. All individuals attending STD clinics or those at high risk for hepatitis B infection (e.g., individuals with multiple sexual partners, sexual partners of individuals with chronic HBV infection, or drug users) should be offered hepatitis B vaccination and advised that they are at high risk for hepatitis B infection (as well as HIV infection) and that they should take steps to reduce that risk (e.g., choosing sexual partners wisely, using condoms, avoiding sharing needles and syringes).

The list of persons who should be vaccinated against hepatitis B is as follows:

• Sexually active homosexual and bisexual men;
• Sexually active heterosexual men and women who have recently been diagnosed with another STD; individuals who have had more than one sexual partner in the past 6 months; STD clinic attendees and prostitutes;
• Drug addicts, including those using injection and non-injection drugs;
• Health workers;
• Recipients of certain donor blood products;
• Persons who have had close household or sexual contact with patients with hepatitis B;
• Visitors from countries where HBV infection is endemic;
• A certain contingent of persons traveling abroad;
• Clients and staff of rehabilitation institutions;
• Patients undergoing hemodialysis.

Antibody screening or vaccination without screening

The prevalence of prior hepatitis B infection among sexually active homosexual men and intravenous drug users is high. The cost/effectiveness of serologic screening of members of these groups to demonstrate prior infection prior to vaccination may be acceptable, depending on the relative costs of laboratory tests and vaccine. Given the current cost of the vaccine, pre-vaccination testing in adolescents is not cost-effective, but pre-vaccination testing is recommended for adults attending STD clinics given the prevalence of hepatitis B. However, given the risk of vaccine refusal from testing prior to vaccination, the first dose of vaccine should be given at the same time as testing. An additional dose of vaccine should be given based on the results of these tests. The preferred pre-vaccination serologic test is the anti-HBs antibody test because it can identify individuals with prior or chronic infection. Since the anti-HBs test will not identify individuals who have been immunized with the vaccine, it is necessary to make appropriate notes about the vaccination in the medical history and ensure that the vaccinated patient is not revaccinated.

Immunization schedule

The hepatitis B vaccine is highly immunogenic and produces protective antibodies after three doses, with different schedules. The most common schedule is to give three doses at 0.1-2 and 4-6 months. The first and second doses should be separated by at least 1 month, and the first and third doses by at least 4 months. If vaccination is interrupted after the first or second dose, the missing dose should be given at the next available opportunity. Vaccination should not be restarted from the first dose if one dose has been missed. The vaccine should be given in the deltoid muscle (not the buttock).

Vaccination after contact with a person infected with viral hepatitis B

Contact with a person with acute hepatitis B

Sexual contact. Persons with acute infection may potentially infect sexual partners. Passive immunization with hepatitis B immune globulin (HBIG) can prevent 75% of these infections. Hepatitis B vaccination alone is less effective in preventing infection than a combination of HBIG and vaccination. Persons who have had sexual contact with persons with acute hepatitis B should receive HBIG and begin serial vaccination within 14 days of the last sexual contact. Anti-HBs testing of sexual partners may be recommended if it does not delay treatment within the 14 days.

Household contact. Household contact with persons with acute hepatitis B does not carry a high risk of infection, except in cases where blood-borne transmission may occur (e.g., through shared toothbrushes or shaving equipment). However, vaccination of household contacts of such patients is recommended, especially children and adolescents. If the patient remains positive for HBsAg after 6 months (i.e., the infection has become chronic), all close household contacts should be vaccinated.

Contact with a person with chronic hepatitis B

Active immunization without the use of HBV-IG is a highly effective method of preventing hepatitis B in individuals who have had household and sexual contact with a patient with chronic hepatitis B. Serological tests after vaccination are indicated for sexual partners of individuals with chronic hepatitis and infants born to HBsAg-positive women.

Special Notes

Pregnancy

Pregnancy is not a contraindication for the administration of HBIG or the vaccine.

HIV infection

Chronic carriage of hepatitis B virus has been observed in HIV-infected patients. The immune response to vaccination in HIV-infected individuals is reduced. Therefore, HIV-infected individuals who are vaccinated should be tested for anti-HBs 1-2 months after the third dose of vaccine. For those who do not mount an immune response to the first vaccination, revaccination with one (or more) doses of vaccine should be considered. Patients who do not mount a response to revaccination should be warned that they may remain susceptible to infection.

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