Annual vaccination against influenza A and B viruses is the most effective method of preventing influenza. An upcoming issue of The Medical Letter will review drugs for chemoprophylaxis and treatment of influenza.

A 23-valent polysaccharide vaccine (PPSV23; Pneumovax 23 - Merck) is the only pneumococcal vaccine approved for use in adults. It has reduced the risk of invasive pneumococcal disease (meningitis or bacteremic pneumonia), but not mortality, in immunocompetent older adults.2 PPSV23 has not been shown to reduce the risk of invasive pneumococcal disease (IPD) in immunocompromised patients.

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The FDA has licensed Adacel (Aventis Pasteur) and Boostrix (GlaxoSmithKline), two new combination vaccines that include tetanus toxoid, diphtheria toxoid and acellular pertussis antigens (Tdap), for use as a booster in adolescents and adults. In the past, older children and adults were not re-immunized against pertussis because of concerns about reactions to the whole-cell vaccine previously used in younger children. The CDC Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) have recommended that either of the new Tdap vaccines replace routine tetanus-diphtheria (Td) boosters in adolescents 11-18 years old, and Adacel should replace Td boosters in adults 19-64 years old.

Annual immunization against influenza A and B is the most effective method of preventing infection and has been shown to reduce associated complications. A future issue of The Medical Letter will review drug prophylaxis and treatment of influenza.

Last year influenza season began in October, peaked in December (both much earlier than usual), and was associated with severe disease, particularly in children. Much of the illness was due to a circulating influenza A H3N2 strain (Fujian type) that had drifted antigenically from the H3N2 strain in the vaccine. The vaccine for the 2004-05 influenza season includes A/Wyoming/3/2003 (H3N2), which is antigenically equivalent to the Fujian strain, A/New Caledonia/20/99 (H1N1), which is unchanged, and a new B strain, either B/Jiangsu/10/2003 or B/Jilin/20/2003, which are both antigenically equivalent to B/Shanghai/361/2002.

Addendum: FluMist Storage: The storage requirements for FluMist, the intranasal live-attenuated influenza vaccine (Medical Letter 2003; 45:65) have changed. New data have shown that frost-free freezers are appropriate for storage for at least 3 months, without need for a freezer-box insert.

FluMist (MedImmune), the first live-attenuated and first intranasally administered influenza vaccine, has been approved by the FDA to prevent influenza in healthy people 5-49 years old. Given as a nasal spray, it stimulates immunity by viral replication in the upper respiratory tract. This vaccine apparently will be advertised directly to the public as a "needle-free" alternative to intramuscular influenza vaccine.

A new pentavalent vaccine (Pediarix - GlaxoSmithKline), licensed by the FDA for children 6 weeks to 7 years old, includes the antigens from vaccines already marketed against diphtheria, tetanus and pertussis (Infanrix) and hepatitis B (Engerix-B), and a new inactivated polio component.

Production problems in some plants have delayed the availability of this year's influenza vaccine and may limit the total supply. These problems appear to be confined to the USA; no shortage is anticipated in Canada

The FDA has approved a conjugate heptavalent pneumococcal vaccine for prevention of invasive pneumococcal disease in infants and children.

A new trivalent influenza vaccine for intramuscular use is available for the 1998-1999 influenza season (Morbid Mortal Weekly Rep, 47, RR-6, May 1, 1998). Last year's vaccine was less effective than usual because of the appearance of a new variant (A/Sydney/5/97) after selection of the vaccine antigens (Morbid Mortal Weekly Rep, 47:196, 1998). Antigens in the current vaccine are A/Beijing/262/95-like (H1N1); A/Sydney/5/97-like (H3N2), and B/Harbin/07/94, antigenically equivalent to B/Beijing/184/93. Both H1N1 and the H3N2 antigens are new this year. A highly publicized live attenuated influenza vaccine given by nasal spray (FluMist) has not yet been approved by the FDA and will not be available in the USA for use in the current influenza season (RB Belshe et al, N Engl J Med, 338:1405, 1998).

A new trivalent influenza vaccine for intramuscular use is available for the 1997-1998 influenza season (Morbid Mortal Weekly Rep, 46 RR-9, April 25, 1997). Antigens in the current vaccine are A/johannesburg/82/96, antigenically equivalent to A/Bayern/07/95 (H1N1); A/Nanchang/933/95, antigenically equivalent to A/Wuhan/359/95 (H3N2); and B/Harbin/07/94, antigenically equivalent to B/Beijing/184/93. Only the H1N1 antigen is new this year. A highly publicized nasal spray flu vaccine still has not been approved by the FDA and will not be available in the USA for use in the current influenza season.

The Centers for Disease Control and Prevention is anticipating a delay, but not a shortage, of influenza vaccine for the 2001-2002 season. Last year manufacturing problems led to a substantial delay in vaccine availability. This years delay is being attributed, in part, to the discontinuation of the Fluogen (King) brand of vaccine. The 2001-02 vaccine will include A/New Caledonia/20/99 (H1N1)-like, A/Moscow/10/99 (H3N2)-like, and B/Sichuan/379/99-like antigens (MMWR Morb Mortal Wkly Rep, 50 RR-4:5, April 30, 2001).

A new trivalent influenza vaccine is available for the 1995-1996 influenza season. Influenza vaccine, made from inactivated virus grown in eggs, is recommended especially for elderly and high-risk patients, their household contacts and health-care personnel who may come in contact with such patients (Morbid Mortal Weekly Rep, 44, RR-3, April 21, 1995). Antigens in the current vaccine are derived from A/Texas/36/91/ (H1N1), A/Johannesburg and B/Harbin antigens are new this year.

A live attenuated varicella vaccine (Varivax - Merck) has been approved for marketing by the US Food and Drug Administration. The Oka/Merck strain used in the vaccine is attenuated by passage in human and embryonic guinea pig cell cultures.

A vaccine to prevent hepatitis A (Havrix - SmithKline Beecham), previously licensed in more than 40 countries, including Canada, is now available in the United States. A similar vaccine manufactured by Merck is investigational in the USA.

Influenza vaccine for the 2002-2003 season will include last year's A strains, A/New Caledonia/20/99 (H1N1)-like and A/Moscow/10/99 (H3N2)-like, and a new B strain, B/Hong- Kong/330/01-like (MMWR Morb Mortal Wkly Rep 2002; 51:503).

The number of immunizations recommended for infants and young children has increased in recent years with the addition of vaccines to prevent Haemophilus influenzae type b infection and hepatitis B (Medical Letter, 33:5, 1991; 34:69, 1992). Now the US Food and Drug Administration has licensed a new vaccine for infants (Tetramune - Lederle-Praxis) that combines a traditional diphtheria, tetanus, and pertussis vaccine (DTP; Tri-Immunol) with a vaccine against Haemophilus influenzae type b (HibTiter).

Masoprocol cream 10% (meso-nordihydroguiaretic acid, Actinex - Reed and Carnrick) is now available in the USA for topical treatment of actinic keratoses.

A new trivalent influenza vaccine is available for the 1993-1994 influenza season. Vaccination may be even more important than usual this year because of the appearance late in last year's flu season of a new antigenic variant, which was associated with an increase in deaths (Morbid Mortal Weekly Rep, 42:385, May 28, 1993). Influenza vaccine is recommended especially for the elderly and high-risk patients, their household contacts, and health-care personnel who may come in contact with such patients (Morbid Mortal Weekly Rep, 42,RR-6, May 14, 1993).

A new trivalent influenza vaccine is now available for the 1992-1993 influenza season (Morbid Mortal Weekly Rep, 41, RR-9:1, May 15, 1992). Vaccination is recommended especially for elderly and high-risk patients, their household contacts, and health-care personnel who may come in contact with such patients. Antigens in the current vaccine are derived from A/Texas/36/91 (H1N1), A/Beijing/353/89 (H3N2), and B/Panama/45/90. The A/Texas/36/91 (H1N1) strain is new this year.

The Immunization Practices Advisory Committee of the US Public Health Service now recommends immunizing all infants and some adolescents against hepatitis B and using a new diphtheria-tetanus-acellular pertussis vaccine (DTaP; ACEL-IMUNE - Lederle) for the fourth and fifth doses of DTP, usually given at 15 to 18 months of age and before school entry (Morbid Mortal Weekly Rep, 40 RR-13:1, November 22, 1991; Morbid Mortal Weekly Rep, 41 RR-1:1, Feb 7, 1992). The Committee on Infectious Diseases of the American Academy of Pediatrics has made similar recommendations but would extend hepatitis B immunization to all adolescents, if possible (Committee on Infectious Diseases, Pediatrics, 89:795, April 1992).

A new trivalent influenza vaccine is now available for the 1991-1992 influenza season (Morbid Mortal Weekly Rep, 40, RR-6:1, May 24, 1991). Vaccination is recommended especially for elderly and high-risk patients, their household contacts, and health-care personnel who may come in contact with such patients. Antigens in the current vaccine are derived from A/Taiwan/1/86 (H1N1), A/Beijing/353/89 (H3N2), and B/Panama/45/90 are new this year.

With the deployment of hundreds of thousands of troops in Saudi Arabia, health problems endemic to the Arabian Peninsula may be coming to the attention of physicians in the USA and other areas.

The US Food and Drug Administration (FDA) recently approved HibTITER (Lederle-Praxis) and PedvaxHIB (Merck), two new Haemophilus influenzae type b conjugate vaccines, for use in infants as part of their primary immunization schedule.

Human rabies continues to be rare in the USA, but animal rabies is becoming more common. An animal epizootic in the mid-Atlantic states, involving especially raccoons, has recently spread into the northeastern states.

A new trivalent influenza vaccine is now available for the 1990-1991 influenza season (Morbid Mortal Weekly Rep, 39, RR7:1, May 11, 1990). Vaccination is recommended especially for elderly and high-risk patients, their household contacts, and health-care personnel who may come in contact with such patients. Antigens in the vaccine include A/Taiwan/1/86 (H1N1), A/Shanghai/16/89 (H3N2), and B/Yamagata/16/88 is new this year.

Six vaccines are recommended for routine use in adults living in the USA (Guide for Adult Immunization, 2nd ed, Philadelphia:American College of Physicians, 1990). Immunization recommendations for travel outside the USA were published in The Medical Letter, volume 32, page 33, April 6, 1990.

A new trivalent inactivated influenza vaccine is now available for the 1989-1990 influenza season (Morbid Mortal Weekly Rep, 38:297, May 5, 1989: Can Med Assoc J, 141:425, Spet 1, 1989). Antigens in this years's Vaccine are A/Taiwan/1/86 (H1N1), A/Shanghai/11/87 (H3N2), and B/Yamagata/16/88. The A/Shanghai and B/Yamagata are new strains this year. The vaccine is available in the USA as a split-virus (subvirion) or whole virus preparation from Squibb (Fluzone), as a split-virus preparation from parke-davis (Fluogen) and Wyeth-Ayerst (Influenza Virus Vaccine, Trivalent), and as a purified-surface-antigen formulations may be less likely to cause adverse reactions, especially in children; whole-virus vaccines may be slighltly more antigenic. Vaccine from previous years should not be used.

In the first six months of 1989, more than 7,000 cases of measles were reported to the US Centers for Disease Control (CDC), a sharp increase over previous years (Morbid Mortal Weekly Rep, 33:456, July 7, 1989). Many of these cases occurred in children and college students who had previously been vaccinated against the disease. Practitioners have asked, therefore, whether their previously immunized young patients should receive a second (or, in some cases, third) immunization against measles.

A new trivalent inactivated influenza vaccine is now available for the 1988-1989 influenza season (Morbid Mortal Weekly Rep, 37:357, June 17, 1988). Antigens in this year's vaccine are A/Taiwan/1/86 (H1N1), A/Sichuan/2/87 (H3N2), and B/Victoria/2/87. The A/Sichuan is a new strain that caused last year's large outbreak of the disease. The vaccine is available in the USA as a split-virus (Subvirion) or whole virus preparation from Squibb (Fluzone), and as a split-virus preparation from Parke-Davis (Fluogen) and Wyeth (Influenza Virus Vaccine, Trivalent). Split-virus vaccines may be slightly more antigenic. Vaccine from previous years should not be used.