[dalke]

"I'm interested to hear why a five minute old infant is at risk of contracting Hep-B. "

Because a baby whose mother is infected with Hep-B can be infected at birth, it's estimated that only 50% of the pregnant women who have Hep-B are identified, and babies can get Hep-B from other family members and caregivers.

See http://www.cdc.gov/mmwr/PDF/rr/rr5416.pdf for the full details, but here are two relevant passages:

> Even with improvements in the management of pregnant women, only approximately 50% of expected births to HBsAg-positive women are identified (on the basis of application of racial/ ethnic-specific HBsAg prevalence estimates to U.S. natality data) for case management, which maximizes timely delivery of postexposure immunoprophylaxis (11; CDC, unpublished data, 2004). The need for proper management of women without prenatal care, including HBsAg testing at the time of admission for delivery and administration of the first dose of vaccine to infants <12 hours of birth, is underscored by the higher prevalence of HBsAg seropositivity among these women than among women who are screened prenatally (12). Even when maternal HBsAg testing does occur, certain infants of HBsAg-positive mothers do not receive postexposure immunoprophylaxis because of testing errors and lapses in reporting of test results (13), and infants of women with unknown HBsAg status at the time of delivery often do not receive a birth dose of vaccine (14).

> Children who are not infected at birth remain at risk from long-term interpersonal contact with their infected mothers. In one study, 38% of infants who were born to HBsAg-positive mothers and who were not infected perinatally became infected by age 4 years (64). In addition, children living with any chronically infected persons are at risk for becoming infected through percutaneous or mucosal exposures to blood or infectious body fluids (e.g., sharing a toothbrush, contact with exudates from dermatologic lesions, contact with HBsAg-contaminated surfaces). HBV transmission rates to susceptible household contacts of chronically infected persons have varied (range: 14%–60%) (65,66). High rates of infection also have been reported among unvaccinated long-term residents of institutions for the mentally handicapped (67,68), and, in rare instances, person-to-person transmission has been reported in child care settings (69,70).

Also, the vaccine is made from virus capsid protein expressed in Baker's yeast. There's no infectious material at all, making it a very safe vaccine. (Unlike the earlier Hep-B vaccine which had a danger of including viral DNA should something go wrong during purification.)

[fnordfnordfnord]

>Because a baby whose mother is infected with Hep-B

Well, we didn't elect to deliver in the back room of a whorehouse, or under a tree on the prairie. We went to one of the best hospitals in the country, where blood tests are done in advance of delivery, where these things are discussed and planned as part of the pre-natal pregnancy care.

Wife and I are both vaccinated, and apparently Hep-B negative. I have to make sure my kids aren't raped by Hep-B positive child-rapists, which is sadly too common.

> There's no infectious material at all, making it a very safe vaccine.

You keep missing something from my posts. I don't doubt the science behind vaccines. You don't need to convince me that vaccines are practically a modern miracle. I lack confidence in manufacturers, and in fairness of the NVIC.

[dalke]

The document I linked you to, "Recommendations of the Advisory Committee on Immunization Practices (ACIP)", does not base its decisions on the number of childhood rapes by people with Hep-B, nor on the "number of babies delivered in the back room of a whorehouse." Why do you believe those are critical factors in the decision?

You seem to think that Hep-B is only spread through sex and drug use, and from the mother through childbirth. This is incorrect. For example, one of the citations in the above report was to http://www.ncbi.nlm.nih.gov/pubmed/2626287 . It seems some 30% of Hep-B infections come from unknown sources.

> We investigated two situations involving hepatitis B virus exposure among children in day care. In the first a 4-year-old boy who attended a day care center developed acute hepatitis B; another child at the center, who had a history of aggressive behavior (biting/scratching), was subsequently found to be a hepatitis B carrier. No other source of infection among family and other contacts was identified and no other persons at the center became infected.

Before the vaccine, some 24,000 children got Hep-C each year. That's down about 90%.

As to the "very safe vaccine", nothing in that last line was meant to imply that you needed any sort of religious faith in vaccines nor that you doubted the science. It was meant to explain why failures by the manufacturer are less likely to lead to severe adverse effects than with the older vaccine. This is an engineering consideration and not a science one.

The previous vaccine was only "safe", and not "very safe." The older vaccine started with blood serum from people who had Hep-B, and purified it so only Hep-B proteins remained. This has a risk of infection should something go wrong in the purification process so that the full virus - or other viruses - somehow get through. This sort of failure would be very risky for newborns.

But the current vaccine, which is based on a genetically modified form of Baker's yeast, does not come from human sources. Since human viruses aren't in the source material, they can't enter the vaccine. There can still be other failure modes, but the most fatal - introduction of virulent particles directly into a newborn baby - can't happen through a process failure during vaccine manufacturing.

Think also of the oral polio virus. This uses an attenuated virus, that is, a mutant form of the polio virus which infects the child, but doesn't cause the symptoms. The child's immune system produces the same antibodies at it would the wild-type virus, which provides immunity. The problem is, the attenuated virus mutates in the body, and it can mutate towards a form which is deadly. This happens about once every 750,000 cases.

Again, this is not the type in the modern Hep-B vaccine - there is no infectious material at all - making it safer than oral polio virus. That's why I said Hep-B is "very safe."

[fnordfnordfnord]

>The previous vaccine was only "safe", and not "very safe." The older vaccine started with blood serum from people who had Hep-B, and purified it so only Hep-B proteins remained. This has a risk of infection should something go wrong in the purification process so that the full virus - or other viruses - somehow get through. This sort of failure would be very risky for newborns.

>But the current vaccine, which is based on a genetically modified form of Baker's yeast, does not come from human sources. Since human viruses aren't in the source material, they can't enter the vaccine. There can still be other failure modes, but the most fatal - introduction of virulent particles directly into a newborn baby - can't happen through a process failure during vaccine manufacturing.

That is interesting and reassuring to learn. Thanks, I will also pass it on to Mrs. Fnord.