Oral poliomyelitis vaccines

organisations representing indigents and immigrants, in an effort to develop tuberculosis control strategies for the USA, and to lobby the government for funding. Reichman’s entire career gives the lie to Wallace’s charge that his Lancet commentary represents a "freezing out of most other disciplines needed for tuberculosis control by biomedical Neil W

Schluger

New York

University School of Medicine, New York, NY 10016, USA

l Wallace D. The resurgence of tuberculosis. Letter 1996; 347: 1115-16. 2 Reichman LB. How to ensure the continued resurgence of tuberculosis. Lancet 1996; 347: 175-77.

poliomyelitis vaccines

Sir - In his March 9 commentary’ on poliomyelitis vaccines Hull makes the following statement about oral poliomyelitis vaccine (OPV): "passive transfer of vaccine virus can protect non-immunised individuals, providing better population immunity". However, in an earlier commentary2 Patriarca puts forward a very different view on OPV: "we now know that secondary spread of vaccine virus to susceptible contacts plays very little part in population immunity". Perhaps further discussion on these two apparently contradictory statements is warranted.

Jeffrey

poliovirus vaccines, Second International Conference. Special publication no 50. Washington DC: Pan American Sanitary Bureau, 1960; 144: 60. 4 5

Hanna

Centre for Disease Control, Tropical Public Health Unit, PO Box 1103, Cairns, Queensland 4870, Australia

Queensland Health,

l Hul HF, Lee JW. Sabin, Salk or sequential? Lancet 1996; 347: 630. Patriarca PA. Polio outbreaks: a tale of torment. Lancet 1994; 344: 630-31

2

Authors’ replies SiR-As all pollsters and politicians know, the answer given depends on what question is asked. There can be no doubt that passive transfer of poliomyelitis vaccine virus occurs and can induce immunity in unvaccinated persons. We note that Patriarca is a co-author of a soon to be published study showing that 9-42% of unimmunised, preschool children in the USA had antibodies against each of the three poliovirus serotypes.’ Aylward and colleagues reported that 94% of Italian gypsies were immune to type 2 poliovirus despite an immunisation coverage of 26%. These studies, as well as the classic studies of Fox, support our contention that live OPV is capable of inducing a higher degree of population immunity than would result from inactivated poliomyelitis vaccine." Patriarca states that secondary spread of vaccine virus plays a minimum role in population immunity. In the

ability of OPV virus to spread from vaccinees to susceptible contacts was conclusively demonstrated nearly 40 years ago during preliminary field trials of Sabin-derived OPV. The most compelling evidence was obtained in southern Louisiana in the USA, in which 33% of seronegative household contacts who were exposed to OPV recipients developed detectable neutralising antibody in the absence of circulation of wild-type poliovirus.’ On the basis of these and other observations, it quickly became dogma that programmes using OPV would result in far higher levels of population immunity than would be expected from

of his full commentary, we understand this to mean passive transfer of vaccine virus to unvaccinated persons cannot be relied upon to interrupt wild poliovirus transmission and that we must seek to immunise every child. We believe that there is no contradiction between our points of view on passive transfer of vaccine virus. We are also in agreement that the global eradication of poliomyelitis should proceed with all due speed.

vaccination alone.

Experiences gained after the advent of aggressive immunisation programmes globally now question the degree to which this dogma might apply to the modern world. First, large gaps in seroimmunity to poliovirus types 1 and 3 have been demonstrated repeatedly in developing countries despite high levels of OPV coverage.2 Second, recent evidence from controlled trials in Brazil and The Gambia suggests that seroconversion rates may actually be lower among OPV recipients who are exposed to other vaccinees living in the same household or housing compound. Third, secondary spread of OPV was recently reconfirmed in the USA, but the effect was recorded almost exclusively in the rare child who had never received OPV, and was limited mainly to poliovirus type 2.4 Secondary immunisation with type 2 viruses is of least concern because of uniformly high antibody responses to Sabin-derived type 2 strains2 and the virtual disappearance of wild-type 2 infections globally.’ These observations do nothing to reduce the extraordinary utility of OPV nor the remarkable success of the mass campaign strategy in the now full-fledged global poliomyelitis eradication initiative. However, they do serve as an important reminder that immunity to poliovirus, like other vaccine-preventable infections, can be best assured by immunising each and every child directly. Peter A Patriarca Center for

Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA 1

2

context

that

*Harry F Hull, Jong

Wook Lee

Global Programme for Vaccines and Immunisation, World Health Organization, Geneva 1211, Switzerland

1 Chen R, Hausinger S, Dajani AS,

et al. Seroprevalence of antibody against poliovirus in inner-city preschool children: implications for vaccination policy in the United States. JAMA (in press). 2 Aylward RB, Porta D, Firore L, Chierchini P, Forastiere F.

Unimmunized gypsy populations and implications for the eradication of poliomyelitis in

Europe. J Infect Dis (in press).

3 Fox JP, LeBlanc DR, Gelfand HM, Clemmer DJ, Potash L. Spread of a vaccine

Hull HF, Lee JW. Sabin, Salk, or sequential? Lancet 1996; 347: 630. Patriarca PA. Polio outbreaks: a tale of torment. Lancet 1994; 344: 630-31.

SiR-The

practitioners".

Oral

Live

strain of poliovirus in southern Louisiana communities. In:

3

4

5

Fox JP, Gelfand HM, LeBlanc DR, Potash L, Clemmer DI, Lapenta D. The spread of vaccine strains of poliovirus in the household and in the community in southern Louisiana. In: Papers and discussions presented at the fifth international poliomyelitis conference. Philadelphia: Lippincott, 1961: 368-83. Patriarca PA, Wright PF, John TJ. Factors affecting the immunogenicity of oral poliovirus vaccine in developing countries: review. Rev Infect Dis 1991; 13: 926-39. World Health Organization Collaborative Study Group on Oral Poliovirus Vaccine. Factors affecting the immunogenicity of oral poliovirus vaccine: a prospective evaluation in Brazil and the Gambia. J Infect Dis 1995; 171: 1097-106. Chen RT, Hausinger S, Dajani AS, et al. Seroprevalence of antibody against poliovirus in inner-city preschool children: implications for vaccination policy in the United States. JAMA (in press). Hull HF, Ward NA, Hull BP, Milstien JB, de Quadros C. Paralytic poliomyelitis: seasoned strategies, disappearing disease. Lancet 1994; 343: 1131-37.

SiR-Hull and Lee (March 9, p 630)’ express concern that a change in polio immunisation policy in the US might adversely affect the global eradication programme, by an vaccination alone is not OPV is an unsafe vaccine". There has been no case of wild virus polio in the US since 1979; there has been no case in the entire Western Hemisphere since August, 1991. However, there have been

interpretation that "oral polio enough to control polio, or that

1495

of vaccine-associated paralytic polio (VAPP) in the USA annually since 1961. Therefore, the consideration of a change in approach for the USA should be regarded in that context. To maintain public support for our multiple immunisation programmes so as to prevent childhood diseases, it is necessary to maintain the confidence of our patients and their parents. The USA abandoned smallpox vaccination in 1971, 6 years before completion of the global smallpox eradication programme. Yet it was never felt that the US cessation in any way compromised or delayed fulfilment of the programme. A change in US polio immunisation practices is highly unlikely to influence the programmes where polio remains endemic (sub-Saharan Africa and Southeast Asia). Despite any change in vaccine policy, US financial support for the global eradication programme should and will continue, hopefully augmented, in the next important years. an

average of 8-2

cases

vaccination before global eradication because of the excess incidence of vaccine adverse effects relative to smallpox diseased Similarly, the continued occurrence of vaccineassociated paralytic poliomyelitis in the absence of wild polio disease for 17 years is driving a shift to the use of a safer combined IPV/OPV strategy. Each country, with its specific vaccine uptake, and incidence of VPD and vaccine adverse effects, needs to arrive at its own strategy based on optimum balancing of risks and benefits. For most countries world wide, where circulation of wild poliovirus still occurs or is a recent memory, an OPV strategy still makes the most sense for control of paralytic poliomyelitis. Robert T Chen Vaccine Safety and Development Activity National Immunisation Programme, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA

1 2

Samuel L Katz Department of Pediatrics, Pediatric Health Policy and Infectious Diseases, Duke University Medical Center, Durham, NC27710, USA

3

4 1

Hull HF, Lee

JW. Sabin, Salk,

or

sequential?

Lancet 1996; 347: 63.

Sir - While not immediately apparent, Hull and Lee’s’ recommendation for most countries to continue giving OPV as the key tool for poliomyelitis eradication is actually consistent with the possible shift by the USA from exclusive use of OPV to greater reliance on inactivated poliovirus vaccine. Immunisation programmes against specific vaccinepreventable disease (VPD) in any country can be seen as an evolutionary process (figure) with a dynamic relation between disease incidence, vaccine uptake, and vaccine adverse effects.2 In the prevaccine era (stage 1), there is only a high incidence of disease. Once immunisation is introduced and vaccine uptake increases, the incidence of VPD is reduced with a small but increasing frequency of adverse effects (stage 2). With sustained high vaccine uptake, the occurrence of adverse effects may approximate and even exceed that of VPD; this may attract the attention of media and antivaccine groups, leading to loss of confidence in the vaccine, drop in vaccine uptake, and resurgence of VPD (stage 3) (as happened with pertussis vaccine in several countries in the 1980s). The resurgence of VPD or development of a safer vaccine may allow return to high vaccine uptake levels and decline in disease (stage 4). For VPD (eg, smallpox and hopefully poliomyelitis) that are eradicated, vaccination can also be stopped with eradication of vaccine adverse effects (stage 5). In this context, it is understandable that the USA rescinded its recommendations for universal smallpox

Figure: Evolution of immunisation programme and prominence of vaccine safety 1496

5

Hull HF, Lee JW. Sabin, Salk, or sequential? Lancet 1996; 347: 630. Chen RT, Rastogi SC, Mullen JR, et al. The vaccine adverse event reporting system (VAERS). Vaccine 1994; 12: 542-50. Krantz I, Taranger J, Trollfors B. Estimating incidence of whooping cough over time. Int J Epidemiol 1989; 18: 959-63. Kimura M, Kuno-Sakai H. Developments in pertussis immunization in Japan. Lancet 1990; 336: 30-32. Center for Disease Control. Public Health Service recommendations on smallpox vaccination. MMWR Morb Mort Wkly Rep 1971; 20: 339-45.

Tonsillectomy in 1913 SIR - Your readers might be interested in my 88-year-old father’s (Cecil Cummins) account of tonsillectomy just before the First World War. He faces a cataract operation as a day case with the same optimism and fortitude that has characterised his life. He remains my only hero. "When I was very young it was the done thing in the cotton broker suburb of Liverpool where I lived for all children to have their tonsils and adenoids removed, lest they should grow up with Diverpood adedoids. One by one we were all taken to a doctor in Rodney Street, who ran what would today be called a production line for this purpose. My mother deemed it fitting that I should wear my best suit, short trousers, and an Eton collar with one of those bow ties that snapped into place and could be spun like a propeller if the collar failed to restrain it. The entire place seemed to be furnished with black horsehair furniture, which scratched the backs of my thighs, possibly to draw attention away from the operation. I was released from the horse-hair chair in the dining room and seated in another in a different room and invited to breathe an objectionable sweet srnell (ether?) When I came to, in yet another horse-hair chair, there seemed to be a dozen or so people crowding around me, all with chopsticks down my throat until one of them said, "Got it!". At this, they all retreated and a nurse-the only one with any semblance of a uniform, not to mention theatre gear-told me to gargle with something, and spit it out. Returned to the first horse-hair chair to recover, the nurse came in and asked if I wanted to "see them". I reluctantly agreed and she returned with a kidney-shaped enamel bowl containing something horrible that looked as if even the butcher had discarded it. The sight of that and the horse-hair discomfort are the high points of this memory, apart from the great moment when one of the chop-stick types gave me my release: "You can put your collar and tie on now. Good bye." A taxi to Exchange Station and a growler from Blundellsands Station followed by new bread and strawberry jam for tea, which did not work and had to be supplanted by "pobs" (bread-andmilk). Eleven till four was not bad!" Brian Cummins 8 St John’s Road, Bathwick, Bath BA2 6PX, UK