document, the committee opted to express its views about the desirable targets for a malaria vaccine in terms of two types of vaccine, a “first-generation vaccine” and an “ideal” vaccine (Table 4-1). The former would be a vaccine worth using by the military in addition to chemoprophylaxis, while the latter represents the most desirable vaccine in all characteristics and could be used to replace the routine use of chemoprophylaxis.

The desired levels of protection specified in Table 4-1 (60 percent for a first-generation vaccine and at least 95 percent for a second-generation vaccine) represent the consensus Delphian judgment of the committee members based on their expert opinion and by analogy with other diseases for which vaccines are being developed. For the first-generation vaccine, there is no objective criterion justifying the level of 60 percent—it represents what the committee felt would likely be useful in addition to chemoprophylaxis.

Vaccine development often follows a “generational” process whereby the first vaccine licensed and marketed is not fully effective, but is later replaced with a second-generation vaccine with greater efficacy, a different schedule, a different target age-group, and/or better safety. This has occurred for example with the Haemophilus influenzae type b (Hib), pertussis, pneumococcal, and hepatitis B vaccines. This adjunctive strategy is very

TABLE 4-1 Important Characteristics of a First-Generation Malaria Vaccine and a Later-Generation Ideal Vaccine

Characteristic

First-Generation Vaccine

Ideal Vaccine

Species

P. falciparum

All malaria species

Efficacy end point

Clinical disease

Blood-stage infection

Level of vaccine efficacya

60%

≥95%

Duration of protection

6 months

3 years

Immunization schedule

Reasonably rapid, convenient, and compatible with concurrent other vaccines

Rapid, convenient, and compatible with concurrent other vaccines

Chemoprophylaxis still required

Yes

No

aThe proposed levels are intended as point estimates. The lower limit for the first-generation vaccine might be of the order of 30–40 percent, by analogy with what is regarded as potentially useful for seasonal influenza and HIV.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement