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HIV Medicine 2005
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Dirk Albrecht and Thomas Weitzel

The increased morbidity and mortality of infectious diseases is a key feature of HIV infection. Vaccination and immunoprophylaxis can make an important contribution to their prevention. In this chapter, we discuss the potential benefits and risks of vaccinating HIV patients, and provide an overview of available vaccines and post-exposure prophylactic measures and their proper use.

Vaccination recommendations should always take into account the national guidelines, which reflect the strategies for preventing infectious diseases that differ sometimes from country to country. Also, the availability of vaccines may vary. This chapter is, to a certain extent, based on the German standards and the vaccines marketed in Germany.

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Assessing potential benefits of a vaccination What is the current status of protection? Is a prior infection documented or likely? Are prior vaccinations documented? Depending on their immune status, a poorer response to previous vaccines and an accelerated decline of protective immunity over time must be expected in HIV patients. Antibody titer controls should be considered more frequently than in healthy individuals. What is the individual risk of acquiring a specific infection? Amongst other things, the medical history should include sexual behavior, contact to people carrying a particular infection, travel, and contact with children. What are the chances of developing protective immunity after vaccination? Poor immune status at the time of vaccination decreases the likelihood of developing a protective response. As a general rule, CD4+ T-cell counts < 300/µl may result in a reduced response to immunization; at < 100/µl significant immunization effects are improbable (Castelli & Patroni 2000). ART-mediated immune reconstitution effects require a dynamic approach to vaccination strategies. Consequently, vaccinations should be reconsidered if CD4+ T-cells rise to > 200/µl in patients on ART. Nevertheless, recent data shows that even after immune reconstitution, the CD4+ T-cell nadir might influence the effectiveness of vaccination (Lederman 2003). On the other hand, ART might have a positive effect on the success of vaccination. Assessing the risk of a vaccination In 1992, the first report of an increased viral load following vaccination was published (Ho 1992). This effect, which reflects the stimulation of cellular immunity, is not apparent in vaccine non-responders, however, it has been observed following various vaccinations including tetanus, pneumococci, influenza, and hepatitis B. Vaccination provoked viral replication peaks one to three weeks later; thus, a routine viral load should not be performed within four weeks of vaccination. Numerous studies demonstrated that these viral load elevations are transient, and immunologically and clinically irrelevant. Nevertheless, activated replication carries the increased risk of viral mutation. In a study in influenza vaccinees, this theoretical concern was confirmed in 2 out of 34 patients whose HIV strains developed new RT- or protease-gene mutations (Kolber 2002). This risk of developing resistant strains might need to be considered in patients with limited therapeutic options. Furthermore, elevations of viral load might lead to an increased risk of materno-fetal transmission during pregnancy. Adverse effects of inactivated vaccines are not increased in HIV patients. In live vaccines, however, the rate of severe infection caused by the vaccine strain itself is increased: life-threatening and fatal complications have been reported following live vaccines, including those for smallpox, tuberculosis, measles, and yellow fever. Consequently, live vaccines were contraindicated in HIV patients. Nowadays, however, this rule does not need to be strictly applied, since the patient's immune status as well as the potential for severe side effects of the particular live vaccine must be considered. Vaccination of contacts Whenever HIV patients are susceptible to vaccine-preventable infections, particular care should be taken to vaccinate close contacts, who, after gaining protective immunity, will not transmit the disease. However, if contacts are vaccinated with certain live vaccines (e.g. oral polio vaccine), the HIV patient is at risk of acquiring vaccine-associated illness. Thus, oral polio vaccination of contact persons is contraindicated and the inactivated vaccine should be used. Secondary transmission of MMR or varicella following vaccination is very unlikely. But, if contacts develop vaccine-associated varicella, the HIV patient should receive acyclovir prophylaxis. Summary The indications and optimal timing for a vaccination depend on individual factors such as the stage of HIV infection and the exposure risk to the particular infectious disease. Patients in the early stages of HIV should be vaccinated as soon as possible. In patients with severe immunodeficiency, active vaccinations rarely generate protective immunity and some are even contraindicated. These patients should be informed about how to avoid exposure, and contacts should be vaccinated. For some agents, passive immunization or post-exposure antibiotic prophylaxis are available. When antiretroviral therapy leads to a sustained rise in CD4 counts, vaccinations should be reconsidered and/or repeated. Vaccinations in HIV-infected children HIV-infected children should be vaccinated according to national children vaccination schedules, with the following exceptions: (1) In children with severe immunodeficiency, as defined by CD4+ T-cell counts < 750/µl (0-12 months old), < 500/µl (1-5 years old), and < 200/µl (> 5 years old), or by relative CD4 counts < 15 %, MMR vaccination is contraindicated. (2) In children with a detectable immune deficit, as defined by relative CD4+ T-cell counts < 25 %, varicella vaccination is contraindicated. A possible strategy to avoid unnecessary live vaccines is to predict their probability of success by measuring the response to other inactivated vaccines: if there is no measurable response to diphtheria/tetanus booster, a benefit from live vaccines such as MMR or varicella is unlikely, even if CD4+ T-cell counts are higher than the above mentioned limits (Tim Niehues, pers. comm.). In these cases, immunoglobulin prophylaxis might be useful. HIV-infected children should receive a series of the 7-valent pneumococcal conjugate vaccine, starting in the third month of life, and supplemented by the 23-valent-polysaccharide vaccine after the second year of life. Postexposure prophylaxis In susceptible individuals, the risk of infection and/or disease severity can be reduced by postexposure prophylactic measures. These include active and passive immunizations as well as chemoprophylaxes. Usually, the time between exposure and beginning prophylactic measures is crucial and should be minimized. Table 2 provides an overview of reasonable postexposure prophylaxis regimens in HIV patients. Practical approach to vaccinations Informed consent HIV patients should be circumstantially informed regarding the benefits and risks of vaccines, with particular attention to HIV-related vaccine problems. The obligation to inform vaccinees follows national recommendations and has been recently summarized in Germany (STIKO 2004). Some countries might require written information material and/or a written informed consent. Vaccine information statements in different languages are available via the Internet (e.g. www.immunize.org). Timing of a vaccination Vaccination should be postponed in the presence of a moderate to severe acute infection; a mild infection might be ignored. Live vaccines such as MMR, varicella or yellow fever have to be given either simultaneously or at least four weeks apart from one another. After a dose of immunoglobulin, live vaccines should not be administered within the following three months. At times when exact viral load measurements are crucial for decisions on ART, all vaccinations should be postponed as they can influence viral replication. Primary vaccination series or booster A primary vaccination schedule is only necessary when no prior vaccination is reported or documented. A past incomplete primary series should be completed, but not repeated. In view of the insufficient data, the monitoring of immune protection by antibody tests should be performed more liberally in HIV patients than in the general population. Route of application Vaccination routes are recommended by the manufacturer of each vaccine. High immunogenicity and few complications make intramuscular injections the preferable route of application for the majority of vaccines. The most recommended site is the deltoid muscle, in infants the anterolateral thigh. Many water-soluble vaccines can also be administered subcutaneously. In hemophiliacs, subcutaneous vaccination followed by thorough compression of the injection site for > 2 minutes usually allows vaccination without the coadministration of clotting factors. Only a few vaccines require subcutaneous injection, including meningococcal polysaccharide, Japanese encephalitis, yellow fever, and varicella vaccines. Intradermal rabies vaccination, which is licensed in some countries, should not be performed in HIV patients due to reduced immunogenicity. Side effects The most common side effects after injection of a vaccine are transient and mild. They include reddening, swelling and pain at the injection site. Occasionally, hours to days after the vaccination, elevated body temperature, headache and malaise are reported. Severe vaccination side effects should be reported to health authorities and/or the vaccine manufacturers. Combining vaccines For both primary vaccination series and booster doses it is recommendable to combine vaccines to minimize patient discomfort as well as cost. With some variations between countries, due to differing licensing status, a growing number of vaccines are available in fixed combinations. Documentation Vaccinations should be documented in the patient's medical records as well as in a vaccination card to be kept by the patient. For the latter, a World Health Organization-recommended form can be ordered either through the WHO or national providers. Full documentation includes brand, manufacturer, and lot number of the vaccine. Details on individual vaccines Tetanus/Diphtheria: Following a primary series during childhood, lifelong protection should be maintained by boostering at regular intervals. Depending on their CD4+ T-cell count, HIV patients have a reduced booster response and an accelerated antibody waning (Moss 2003). According to a Danish study (Kurtzhals 1992) and our own experiences in Germany, adult HIV patients frequently have insufficient protection against diphtheria. Whenever possible, tetanus-diphtheria combination vaccines should be used, which, in Germany, are also available in combination with polio and/or pertussis. In the context of a rising incidence of pertussis in adolescents and adults, boostering with acellular pertussis vaccine in adolescents has recently been recommended, and is under discussion for adults (Halperin 2005). Since the adult pertussis booster vaccines are exclusively available in the above-mentioned combinations in Germany as well as in other countries, their use should be considered when tetanus/diphtheria vaccines are given. Pneumococcal: HIV patients have an increased risk of invasive pneumococcal infections (Hirschtick 1995). However, in patients with CD4+ T-cell counts < 500/µl, the response to pneumococcal polysaccharide vaccine was decreased (Weiss 1995), and a double-dose booster did not induce a better response (Rodriguez-Barradas 1996). Similar observations were made with the conjugate vaccine in HIV-infected adults and children (Ahmed 1996, Mahdi 2005). However, the pneumococcal vaccine seems to protect from invasive infections (Breiman 2000, Grau 2005). Confusing data arose from a prospective randomized study on 1,392 HIV patients in Uganda, which reported an increased incidence of pneumococcal infections in the vaccine group (French 2000). Selective destruction of activated B-cell clones, hypothesized to be the underlying mechanism, could not be verified by further investigations (French 2004). Remarkably, long-term follow-up of the initial patient collective showed reduced mortality in the vaccine group, making the assessment of the effects of pneumococcal vaccination in an African setting on patients without ART even more difficult (Watera 2004). According to current recommendations, HIV patients with CD4+ T-cells > 200/µl should receive pneumococcal vaccination as early as possible after their HIV diagnosis. In patients with CD4+ T-cell counts < 200/µl, the effectivity of the vaccine is uncertain, but vaccination should be considered. If, in the course of ART, CD4+ T-cells rise to a stable count of > 200/µl, pneumococcal vaccination should be repeated. Infants from 3 months to 2 years of age should be vaccinated with the 7-valent conjugate vaccine, supplemented by the 23-valent polysaccharide vaccine at age > 2 years. An interval of > 2 months should be kept between the two vaccines. Influenza: Among HIV patients, an increased incidence of influenza has not been found, but complications and severe courses are more common and increased mortality has been observed (Lin & Nichol 2001). Several studies documented a good tolerability of the vaccine in HIV patients (Zanetti 2002). Thus, yearly vaccination at the beginning of the influenza season is recommended for all HIV patients older than six months. In children under ten years of age, the first vaccination should include two doses at a 4-week interval. When CD4+ T-cells are < 100/µl, a response is rarely measurable, and it is unclear whether the benefit outweighs the cost (Rose 1993). The intranasal live vaccine is contraindicated in HIV patients. Hepatitis B: HIV/HBV coinfection is a common problem with dual adverse effects since both the risk of chronic HBV infection and the risk of severe HIV-related complications are increased. Thus, all HIV patients seronegative to HBV should be vaccinated (Laurence 2005). The vaccination response rate and durability, being generally reduced in HIV patients, correlate with CD4+ T-cell counts. Vaccination should thus be performed early following the diagnosis of HIV, and possibly be repeated following immune reconstitution caused by ART. The immune response should be monitored by anti-HBs levels 4-8 weeks after the last dose: anti-HBs levels > 100 IE/l indicate protective immunity; a booster should be performed after ten years. With levels < 100 IE/l, the response is inadequate and an immediate booster should be performed followed by another antibody control. Persistent non-responders should be vaccinated with higher doses of antigen, which are recommended for dialysis patients and other forms of immunosuppression (Poland 2004). High dose hepatitis B vaccines might be useful as first-line vaccines in HIV patients (Fonseca 2005), but more studies are needed for general recommendations. Hepatitis A: This infection is common among HIV patients, but HIV usually causes little aggravation of its course. In a French HIV cohort, 5.8 % acquired acute hepatitis A per year (Fonquernie 2001). The vaccine is indicated in patients with chronic liver disease or increased risk of exposure, e.g. MSM, hemophiliacs, travelers to high-prevalence regions. Routine pre-vaccination serology (HAV IgG) is not generally recommended, but can be considered in patients with possible prior exposure (e.g. Germans born before 1950). A combination with HBV is available and reduces costs. Measles: As measles can cause severe disease in HIV patients, susceptible patients should be vaccinated whenever possible. The status of protection should be checked prior to trips in endemic areas. Unless two vaccinations are documented, a serological test should be performed. In the US, persons born before 1957 are considered immune. The MMR vaccine is used in Germany, but this is contraindicated in symptomatic HIV infection and/or with CD4+ T-cell counts < 200/µl or < 14 % (in children: age-specific thresholds). For susceptible patients, post-exposure immunoglobulin is indicated in certain high-risk situations even prior to exposure. Yellow fever: Information on the effectivity and safety of yellow fever vaccine in HIV patients is only available from < 50 patients, all with CD4+ T-cell counts > 200/µl (Goujon 1995, Receveur 2000, Tattevin 2004). These limited data indicate good tolerability, but reduced rates of seroconversion. One case report describes fatal encephalitis in a patient with a low CD4+ T-cell count, who was asymptomatic at the time of vaccination (Kengsakul 2002). International recommendations state that vaccination is possible in asymptomatic HIV patients with CD4+ T-cell counts > 200/µl. Due to reduced response rates, titer controls might be useful. We recommend the documentation of seroconversion in a paired serum sample (before, and 2-3 weeks after vaccination). If vaccination is contraindicated, a medical waiver should be issued to patients traveling to countries where yellow fever vaccination is mandatory. However, if there is a substantial risk of exposure, unvaccinated patients should be advised to abandon the journey. Table 1: Vaccines and their indications1 Vaccine type Schedule2 Indication2 Comments Cholera3 inactivated + toxoid primary: 2x (d 0, wk 1-6) protection: 2 y travelers with high risk of exposure5 also limited protection against some forms of travelers' diarrhea Diphtheria toxoid primary: 3x (d 0, wk 4-8, mth 6-12) boost every 10 y generally recommended reduced dose after 6th year of life Hemophilus influenzae b (HiB) polysaccharide primary: according to childhood schedule generally recommended in childhood booster: not routine Incidence of HiB infections in HIV patients low Hepatitis A inactivated primary: 2x (d 0, mth 6) boost after 10 y chronic liver disease increased risk of exposure (e.g. MSM, hemophilia, travel to endemic area) Hepatitis B recombinant antigen primary: 3x (d 0, wk 4, mth 6) boost after 10 y or according to antibody level generally recommended in childhood generally recommended in HIV patients Influenza3 inactivated/ fractionated antigen 1x per year generally recommended in HIV patients year-specific antigen combination according to WHO Japanese encephalitis inactivated primary: 3x protection: 3 y travelers with high risk of exposure5 Measles live attenuated children: 2x adults: 1x generally recommended in childhood susceptible HIV-patients5 travelers to endemic area recommended only in asymptomatic HIV-infection and CD4 > 200/µl (> 14 %) Meningococcal (groups A, C, W135, Y) I. 4-valent polysaccharide II. 4-valent conjugate 1x immunodeficiency (e.g. complement deficiencies, asplenia) travelers with high risk of exposure5 no protection against serotype B (high prevalence in Europe and Brazil) mandatory for pilgrims to Saudi-Arabia some countries: recommended for children, students Mumps live attenuated children: 2x adults: 1x generally recommended in childhood susceptible persons5 with frequent contact to children HIV: recommended only in asymptomatic HIV infection and CD4 > 200/µl (> 14 %) Pertussis purified acellular antigens primary: according to childhood schedule boost: 1x in 11th to 18th year of life generally recommended in childhood increased risk of exposure (e.g. hospital personnel, childcare facilities): boost every 10y some countries may change their strategy to general recommendation for lifelong booster Pneumococcal I. 23-valent polysaccharide II. 7-valent conjugate I: primary: 1x boost every 6 y II: in children only 1x - 4x depending on age general recommendation for HIV patients I: 2 years and older II: 2 months and older; no advantages to I in adults protection only against subset of the naturally occurring strains Poliomyelitis3 inactivated primary: 4x (according to child-hood schedule) boost: 1x in 11th to 18th year of life children: generally recommended adults: increased risk of exposure (e.g. health care, travel to endemic areas): boost after 10 y avoid live vaccine (OPV) in HIV patients and their contacts Rabies inactivated primary: see manufacturer protection: 3-5 y occupational risk of animal contact travelers with high risk of exposure4 HIV: often poor response, serological testing recommended, no intradermal vaccination Rubella live attenuated children: 2x adults: 1x generally recommended in childhood susceptible persons5 with frequent children contact women of child-bearing age HIV: recommended only in asymptomatic HIV infection and CD4 > 200/µl (> 14 %) Smallpox live attenuated Controversial HIV infection is contraindication for prophylactic vaccination HIV patients should avoid contact with vaccinees for 2 weeks (risk of transmission of vaccine strain) Tetanus toxoid primary: 3x (d 0, wk 4-8, mth 6-12) boost every 10 y generally recommended Tick-borne encephalitis inactivated primary: 3x (d 0, mth 1-3, mth 9-12) (accelerated: d 0, d 7, d 21) boost according to manufacturer inhabitants of/travelers to endemic regions with risk of tick exposure consider regional distribution profile European TBE vaccine is probably protective against RSSE (Hayasaka D 2001) Tuberculosis live BCG-strain 1x in newborns not recommended in Germany HIV is a contraindication Typhoid fever3 polysaccharide 1x travelers with high risk of exposure4 Varicella live attenuated age 11 mths-12 y: 1x age > 12 y: 2x (> 6 wks apart) generally recommended in childhood/adolescence susceptible persons5 with frequent contact to children or immunosuppressed patients women (child-bearing age) HIV: not licensed for HIV patients; vaccination can be considered in asymptomatic patients with CD4 > 25 % Yellow fever live attenuated 1x (> 10 d prior to possible exposure) protection: 10 y travelers to endemic areas travel requirements in some countries! vaccination only in authorized institutions HIV: asymptomatic HIV-infection and CD4 > 200/µl Notes d = day, wk = week, mth = month, y = year 1. Also observe national vaccination guidelines and manufacturer's recommendations 2. Schedules and indications mainly adapted to standards and available vaccines in Germany. Strategies in other countries may vary. 3. Live vaccine also available, but not recommended in HIV patients 4. Disease specific definitions. If in doubt, seek travel advice. 5. Susceptible: No documented history of the disease, no prior vaccination, no specific antibodies in serological test. Table 2: Postexposure vaccines and chemoprophylaxes Disease type of prophylaxis Indication Comments Diphtheria I. active immunization II. chemoproph. close / face-to-face contact with a case patient I. if last vaccination > 5 y II. independent of immunization status II: e.g. erythromycin 4x 500 mg/d x 7-10 d Hemophilus influenzae b chemoproph. patients with immunosuppression or persons from their close environment after close contact with a case patient rifampicin 1x 600 mg/d x 4 d Hepatitis A I. active immunization II. simultaneous immunoglobulin I: every exposure of a susceptible1 person II: additionally in patients at risk of severe course (e.g. HBV- or HCV-infection) Hepatitis B I. active immunization/booster II. simultaneous immunoglobulin5 protection status after percutaneous exposure2: insufficient: I+II partial: I complete: not needed Influenza I. active immunization II. chemoproph. I: community outbreak with strain covered by vaccine II: direct exposure of any unvaccinated HIV patient; in patients with severe immunodepression independent of their immunization status II: Influenza A: amantadine 2x 100 mg/d (> 65 years: 1x 100 mg/d) Influenza A or B: oseltamivir: 1x 75 mg/d for details see ACIP (Harper 2005) Measles I. active immunization/booster II. (simultaneous) immunoglobulin5 I: exposure of a susceptible1 person II: exposure of a susceptible1 person with more than mild immunosuppression, when response to active immunization is unlikely or immunization is contraindicated active immunization within 72 hours of exposure consider contraindications for vaccination! Meningococcal I. active immunization II. chemoproph. following an index case: I: according to health authorities II: all household members; persons in contact with oropharyngeal secretions; close contacts in child-care centers, dormitories II: rifampicin 2x 600 mg/d x 2 d or ciprofloxacin 1x 500 mg or ceftriaxone 1x 250 mg i.m. Mumps active immunization exposure of a susceptible1 person active immunization within 3 (-5) days of exposure consider contraindications for vaccination! Pertussis I. active immunization II. chemoproph. I: exposure and incomplete immunization II: close contacts, e.g. household contacts chemoprophylaxis within 7 days of exposure erythromycin 4x 500 mg/d x 14 d (alternatively: clarithromycin, cotrimoxazole) Polio I. active immunization any exposure independent of immunization status avoid delays! Rabies I. active immunization/booster II. simultaneous immunoglobulin5 according to national or local recommendations HIV: consider double dose of active vaccine on day 0, consider immunoglobulin more liberally in immunosuppressed patients Rubella active immunization exposure of a susceptible1 person active immunization is indicated within 5 days of exposure consider contraindications for vaccination! Tetanus I. active immunization/booster II. simultaneous immunoglobulin5 I: vaccine status unknown, incomplete primary series or last booster > 5 years ago II: unknown, 0 or 1 dose of primary series or 2 doses of primary series and > 24 hours between injury and booster after minor, clean wounds: booster only if last is > 10 years ago; simultaneous immunoglobulin not needed Tuberculosis chemoproph. HIV patient after contact with open TB case treat in analogy to latent TB (see TB chapter) Varicella I: active immunization II: simultaneous immunoglobulin5 III: chemoproph. I: chickenpox exposure3 of a susceptible1 patient; zoster exposure4 of a susceptible1 patient II: exposure3,4 of a susceptible1 patient with more than mild immunosuppression < 96 hours after exposure III: exposure3,4 of a susceptible1 patient with more than mild immunosuppression > 96 hours after exposure I: up to 5 days after exposure or 3 days after beginning of exanthema; consider contraindications! III: limited data on prophylactic acyclovir (see Hambleton 2005) Notes 1. susceptible: No documented history of the disease, no prior vaccination, no specific antibodies on serological testing. 2. hepatitis b protection status: (if available within 48 hrs, test anti-HBs titer) complete: good responder and last dose < 5 years ago; or anti-HBs > 100 IE/ml within the last 12 months partial: good responder and last dose > 5, but < 10 years ago; or current anti-HBs documented > 10 (but < 100) IE/ml insufficient: anything less than partial or complete protection good responder: anti-HBs documented > 100 IE/ml after primary series 3. chickenpox exposure: face-to-face contact, household contact, > 1 hour in the same room. 4. zoster exposure: direct contact with skin lesions or their secretions. 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