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Vaccines for Japanese encephalitis
THE LANCET
immunisation remains the best current approach for most of the endemic area.1 Mark C Steinhoff Departments of International Health and Paediatrics, Johns Hopkins University, Baltimore, MD 21205, USA
1
Vaughn DW, Hoke CH. The epidemiology of Japanese encephalitis: prospects for prevention. Epidemiol Rev 1992; 14: 197–221.
SIR—Steinhoff’s June 8 commentary1 pointing out the economic attractiveness of the effective Chinese-made liveattenuated viral vaccine against Japanese encephalitis requires correction in one important detail. He states that the production of the SA 14-14-2 vaccine “in standard cell lines used for vaccine production such as Vero or human diploid cells would increase its acceptability for licensing authorities in many countries”. As the vaccine quality control community knows only too well, live-attenuated viruses cannot be moved from one cell system to another without creating essentially a new vaccine. This vaccine would then have to be retested in man for immunogenicity, safety, and efficacy. Not only is this expensive, but also there is no guarantee that this new vaccine will be acceptable. The SA 14-14-2 vaccine enjoys distinguished company since most licensed viral vaccines are manufactured in cells obtained directly from animals. The challenge that the Chinese manufacturers must meet to gain acceptability for their vaccine is to show that primary hamster kidney cells are as safe for human beings as the other primary cell culture substrates used for vaccine production—eg, chick embryo, rabbit kidney, dog kidney, or monkey kidney cells; this should not be particularly difficult to do. Scott B Halstead National Naval Medical Center, Bethesda, MD 20889-5606, USA
Figure: Spiral CT angiograms of right (top) and left (bottom) modified Blalock-Taussig shunts Ao=aortic arch. Arrow shows stenotic lesions. *Shunts.
1
Steinhoff MC. Japanese encephalitis: a Chinese solution? Lancet 1996; 347: 1570–71.
Spiral CT scanning angiography for assessing systemic-to-pulmonary shunt in children SIR—Systemic to pulmonary shunts are done to improve systemic oxygen saturation and accelerate the development of the pulmonary arteries in neonates and infants with congenital cyanotic heart disease and diminished pulmonary blood flow. Assessment of the shunt graft usually requires invasive angiography. Spiral computed tomography (CT) is a non-invasive technique to produce three-dimensional angiographic images which can be viewed from any perspective.1–3 We evaluated the efficacy of spiral CT angiography for assessing systemic to pulmonary shunts compared with conventional angiography. Eight children (3–18 years old, mean 8·8) with modified Blalock-Taussig shunts (prosthetic grafts between the subclavian and pulmonary arteries) had spiral CT angiography 1–2 weeks before cardiac catheterisation to assess graft patency and indications for further surgery. They were selected at random and informed consent was obtained. Spiral CT angiography was done with a Somatom Plus-S CT scanner (Siemens Medical Systems, Iselin, NJ, USA) with a 4 mm/s table feed velocity. The section thickness was 3 mm, and a section was reconstructed every 2 mm. Imaging was started 20 s after intravenous bolus injection (3 mL/sec) of iopamidol (300 mgI/mL), 2–4 mL/kg. The data was transferred to an independent workstation for threedimensional reconstruction of grafts with a Siemens software
Vol 348 • August 3, 1996
package. The reconstructions were rotated to evaluate stenotic changes. The diameter of grafts was measured with digital computer-assisted calipers (Digitizer KD 4300, Graphtec Co, Japan). Shunt grafts were clearly identified with spiral CT angiography (figure) in all cases. A strong linear correlation between spiral CT angiography and conventional angiography (Y=1·50–2·28, r 2=0·93) was found for measurement of the mid-portion diameter of the shunt graft. In four of eight cases, significant stenotic lesions were observed in the angiographic images at the junction of the shunt graft and pulmonary artery, and a strong linear correlation (Y=1·00–0·62, r 2=0·82) was also observed in the narrowest diameter of the graft between both angiograms. Spiral CT angiography evaluates graft configuration and diameter, with an accuracy similar to that of conventional invasive angiography. *Kenji Hamaoka, Seiichiro Ozawa, Fumiaki Sutou, Z enshiro Onouchi Division of Pediatrics, Children’s Research Hospital, Kyoto Prefectural University of Medicine, Kyoto 602, Japan
1
2
3
Kalender WA, Seissler W, Klota E, Vock P. Spiral volumetric CT with single-breath-hold technique, continuous transport, and continuous scanner rotation. Radiology 1990; 176: 181–83. Rubin GD, Dake MD, Napel SA, McDonnell CH, Jeffrey RB Jr. Three-dimensional spiral CT angiography of the abdomen: initial clinical experience. Radiology 1993; 186: 147–52. Dillon EH, van Leeuwen MS, Fernandez MA, Mali WPTM. Spiral CT angiography. AJR 1993; 160: 1273–78.
341
immunisation remains the best current approach for most of the endemic area.1 Mark C Steinhoff Departments of International Health and Paediatrics, Johns Hopkins University, Baltimore, MD 21205, USA
1
Vaughn DW, Hoke CH. The epidemiology of Japanese encephalitis: prospects for prevention. Epidemiol Rev 1992; 14: 197–221.
SIR—Steinhoff’s June 8 commentary1 pointing out the economic attractiveness of the effective Chinese-made liveattenuated viral vaccine against Japanese encephalitis requires correction in one important detail. He states that the production of the SA 14-14-2 vaccine “in standard cell lines used for vaccine production such as Vero or human diploid cells would increase its acceptability for licensing authorities in many countries”. As the vaccine quality control community knows only too well, live-attenuated viruses cannot be moved from one cell system to another without creating essentially a new vaccine. This vaccine would then have to be retested in man for immunogenicity, safety, and efficacy. Not only is this expensive, but also there is no guarantee that this new vaccine will be acceptable. The SA 14-14-2 vaccine enjoys distinguished company since most licensed viral vaccines are manufactured in cells obtained directly from animals. The challenge that the Chinese manufacturers must meet to gain acceptability for their vaccine is to show that primary hamster kidney cells are as safe for human beings as the other primary cell culture substrates used for vaccine production—eg, chick embryo, rabbit kidney, dog kidney, or monkey kidney cells; this should not be particularly difficult to do. Scott B Halstead National Naval Medical Center, Bethesda, MD 20889-5606, USA
Figure: Spiral CT angiograms of right (top) and left (bottom) modified Blalock-Taussig shunts Ao=aortic arch. Arrow shows stenotic lesions. *Shunts.
1
Steinhoff MC. Japanese encephalitis: a Chinese solution? Lancet 1996; 347: 1570–71.
Spiral CT scanning angiography for assessing systemic-to-pulmonary shunt in children SIR—Systemic to pulmonary shunts are done to improve systemic oxygen saturation and accelerate the development of the pulmonary arteries in neonates and infants with congenital cyanotic heart disease and diminished pulmonary blood flow. Assessment of the shunt graft usually requires invasive angiography. Spiral computed tomography (CT) is a non-invasive technique to produce three-dimensional angiographic images which can be viewed from any perspective.1–3 We evaluated the efficacy of spiral CT angiography for assessing systemic to pulmonary shunts compared with conventional angiography. Eight children (3–18 years old, mean 8·8) with modified Blalock-Taussig shunts (prosthetic grafts between the subclavian and pulmonary arteries) had spiral CT angiography 1–2 weeks before cardiac catheterisation to assess graft patency and indications for further surgery. They were selected at random and informed consent was obtained. Spiral CT angiography was done with a Somatom Plus-S CT scanner (Siemens Medical Systems, Iselin, NJ, USA) with a 4 mm/s table feed velocity. The section thickness was 3 mm, and a section was reconstructed every 2 mm. Imaging was started 20 s after intravenous bolus injection (3 mL/sec) of iopamidol (300 mgI/mL), 2–4 mL/kg. The data was transferred to an independent workstation for threedimensional reconstruction of grafts with a Siemens software
Vol 348 • August 3, 1996
package. The reconstructions were rotated to evaluate stenotic changes. The diameter of grafts was measured with digital computer-assisted calipers (Digitizer KD 4300, Graphtec Co, Japan). Shunt grafts were clearly identified with spiral CT angiography (figure) in all cases. A strong linear correlation between spiral CT angiography and conventional angiography (Y=1·50–2·28, r 2=0·93) was found for measurement of the mid-portion diameter of the shunt graft. In four of eight cases, significant stenotic lesions were observed in the angiographic images at the junction of the shunt graft and pulmonary artery, and a strong linear correlation (Y=1·00–0·62, r 2=0·82) was also observed in the narrowest diameter of the graft between both angiograms. Spiral CT angiography evaluates graft configuration and diameter, with an accuracy similar to that of conventional invasive angiography. *Kenji Hamaoka, Seiichiro Ozawa, Fumiaki Sutou, Z enshiro Onouchi Division of Pediatrics, Children’s Research Hospital, Kyoto Prefectural University of Medicine, Kyoto 602, Japan
1
2
3
Kalender WA, Seissler W, Klota E, Vock P. Spiral volumetric CT with single-breath-hold technique, continuous transport, and continuous scanner rotation. Radiology 1990; 176: 181–83. Rubin GD, Dake MD, Napel SA, McDonnell CH, Jeffrey RB Jr. Three-dimensional spiral CT angiography of the abdomen: initial clinical experience. Radiology 1993; 186: 147–52. Dillon EH, van Leeuwen MS, Fernandez MA, Mali WPTM. Spiral CT angiography. AJR 1993; 160: 1273–78.
341