FRIDAY, June 6 (HealthDay News) -- The popular painkiller codeine can be ineffective or, worse, cause serious reactions if you are among those people whose bodies do not process the medication properly.

The liver converts codeine into morphine using the enzyme CYP2D6, a process that causes pain relief in most people. However, genetic differences in some people cause either too much or too little of the enzyme to be produced, resulting in less than pleasant results, reports Public Citizen, a national, nonprofit consumer advocacy group, in its June Worst Pills, Best Pills newsletter.

People whose liver's produce higher than normal CYP2D6 levels convert more of the codeine into morphine -- a situation that could cause excessive sedation, severe constipation and other side effects. While this only occurs in about 4 percent of Caucasian North Americans, prevalence is much higher in people from Greece and Portugal (10 percent), Saudi Arabia (20 percent) and Ethiopia (30 percent).

People with less CYP2D6 find little or no relief from codeine, because the liver does not convert enough into morphine. This happens in about 6 percent to 10 percent of Caucasians, 3 percent to 6 percent of Mexican-Americans, 2 percent to 5 percent of African-Americans and about 1 percent of Asians.

"When one adds the number of people who are genetically deficient in CYP2D6 to the number of people taking medications that inhibit CYP2D6, it is clear that a significantly large group of people are at risk of a suboptimal response to codeine," Sidney Wolfe, director of Public Citizen's Health Research Group, said in a prepared statement.

Certain medications can also affect one's CYP2D6 activity. The enzyme's production is inhibited, for example, by: diphenhydramine, a common antihistamine sold over-the-counter as Benadryl; and quinidine, a medication used to treat abnormal heart rhythm and sold under the brand names Duraquin, Quinaglute, Dura-tabs, and Quinidex, the report said.

Testing one's CYP2D6 enzyme level is neither routinely available nor affordable, so patients taking codeine for the first time should use caution and watch for signs of an excessive response, such as sedation, respiratory depression and gastrointestinal effects, Wolfe said.

"All inadequate or excessive responses to this drug need to be reported to a physician," Wolfe said.

More information

The U.S. National Library of Medicine has more about codeine.

WEDNESDAY, June 11 (HealthDay News) -- Scientists have succeeded in developing a whole-virus bird flu vaccine that appears to be safe, more effective than the one currently approved for human use and also able to be manufactured much more quickly than conventional vaccines.

Three-quarters of volunteers produced antibodies against the virus after receiving a second dose of the vaccine, CELVAPAN, made by Baxter, compared with only 45 percent in the currently approved vaccine.

Importantly, the study confirms the feasibility of using new, cell culture-derived vaccine.

"The fact that they were able to do this, and very efficiently, and get such good antibody response reinforces and reconfirms that, even for the annual flu virus, we need to move away from embryonated hens' eggs [the current method for producing vaccines] and move to cell cultures," said Dr. Pascal James Imperato, dean of the graduate program in public health at the State University of New York (SUNY) Downstate Medical Center in New York City and a former New York city health commissioner.

"We don't know if [the bird flu] ever really did become a pandemic [what protection this would afford]," Imperato added. "But this gives us some reassurance that there would at least be a mechanism to rapidly produce this vaccine."

"CELVAPAN is unique in that it provides protection among several bird flu virus strains, can be produced in about less than half the time of traditional methods and does not require an additive to boost an immune response," said study author Dr. Hartmut J. Ehrlich, vice president of Baxter Global Research & Development, in Vienna.

"Baxter has submitted for licensure with the EMEA [European Medicines Agency] and has two programs with the U.S. government for flu vaccine development for the U.S. market," Ehrlich said. "Additionally, Baxter is working with health authorities around the world to help them prepare for a pandemic. Baxter partners with governments on research and development, offers a vaccine stockpile and capacity planning to be used in the event a pandemic is declared. Several governments have already received stockpiles and have made advance purchases of capacity."

The hunt for a good bird flu vaccine to be used in humans has gone on for some 10 years, since the H5N1 family of avian flu first emerged in Hong Kong, said the author of a perspective accompanying this latest study, both published in the June 12 issue of the New England Journal of Medicine.

In the past two years, the H5N1 strain of avian flu has infected poultry throughout Southeast Asia, Central Asia, Africa and Europe, prompting the destruction of millions of birds. So far, more than 100 people have died worldwide from H5N1 infection, which has been spread through close contact with birds.

Experts fear that the virus will acquire the ability to jump easily between humans, leading to a pandemic and millions of deaths. Unlike the seasonal flu, humans have no immunity to bird flu.

Last year, the U.S. Food and Drug Administration approved an admittedly less-than-perfect vaccine against bird flu, the first such vaccine to be approved for humans. At the time, the vaccine was described as an "interim measure."

Producing and distributing enough vaccine to protect large populations is a key problem.

For the past 50 years, vaccines have been made using a cumbersome egg-based technology, which requires weakened virus injected into hundreds of millions of fertilized hens' eggs each year. The process takes about six months to be completed and has to be repeated as virus strains change.

The Vero cell technology used here uses "wild type" virus (the strains existing in nature) grown directly in cell culture, allowing more of the vaccine to be produced in a shorter amount of time (about 12 weeks).

The vaccine also didn't need an adjuvant, a substance added to a vaccine to make it stronger. There have been safety concerns about adjuvants.

Researchers were also able to use a whole virus, thought to produce better immunity responses, without any major side effects.

"We had been concerned with the idea that whole viruses have more side effects, but this doesn't show that," said Dr. Marc Siegel, an associate professor of medicine at New York University School of Medicine, and author of Bird Flu: Everything You Need to Know About the Next Pandemic.

CELVAPAN was tested on 275 adults aged 18 to 45, all of whom received two doses 21 days apart. Not only did the vaccine produce an immune response against the A/Vietnam/1203/2004 virus strain, but also against two related strains.

With all the successes demonstrated here, experts still point to some caveats. One is that the vaccine was only tested in younger adults (up to 45 years of age), not older adults where it would be most needed.

"We don't know how older adults would respond in terms of antibody levels," Imperato said. "We know that younger adults tend to form antibodies to influenza vaccines much better than older adults."

Having to give two doses is also a drawback. "As soon as you have to give two doses of a vaccine, even if it's not at a very long interval, it presents a problem with public compliance," Imperato said.

And there are many who believe bird flu will not result in a major threat to humans. "I still think there's no reason to believe that a virus that's so pathogenic to birds is automatically going to become pathogenic to humans," Siegel said. "In fact, most pandemics come from low-pathogenic viruses. We've got to watch this carefully, because it's such a killer [mortality rate is upwards of 60 percent in humans], but that doesn't mean by any stretch of imagination that it's going to become a human virus."

More information

The U.S. Centers for Disease Control and Prevention has more on bird flu.

WEDNESDAY, May 28 (HealthDay News) -- Here's another reason why adults shouldn't smoke around kids:

In addition to developing asthma and respiratory infections, children in households where someone smokes are more likely to catch a whole range of severe infections, including meningococcal disease. Many even have to be hospitalized, a new study found.

Being around smoke during the first few months of life was most dangerous, especially if the newborn was born underweight or premature.

"This is just adding to the list of why people should not be smoking," said Dr. Len Horovitz, a pulmonary specialist with Lenox Hill Hospital in New York City. "It's probably that smoking is not just a respiratory irritant, but many things in smoke affect the immune system."

The ill effects of secondhand smoke on people of all ages is well known. As more bans are put in place, children -- and others -- are exposed less and less to secondhand smoke in public places. But secondhand smoke in the home is another matter, according to the study authors, from the University of Hong Kong, whose findings are published online May 28 in the journal Tobacco Control.

The researchers followed 7,402 children born in Hong Kong in April and May of 1997 (representing almost 80 percent of all children born in Hong Kong during that time period) until they turned 8 in 2005.

Exposure to secondhand smoke within a distance of three meters (9.8 feet) in early life was associated with a 14 percent increased risk of being hospitalized for infectious diseases up until the age of 8.

And exposure to secondhand smoke during a baby's first six months of life increased the likelihood of a hospitalization by 45 percent by the time the child was 8. Babies born prematurely were twice as likely to be hospitalized, while those born with a low birth weight were 75 percent more likely to be hospitalized during the first eight years of life, the study found.

Children born to younger, poorer mothers were more likely to be exposed to secondhand smoke.

"The major strength of the study is that it was done in Hong Kong where they can follow 80-plus percent of a birth cohort," said Dr. Norman Edelman, chief medical officer of the American Lung Association. "The respiratory findings are not new, the other infections are."

The study authors speculate that secondhand smoke may affect the immune system, making infants, toddlers and young children more susceptible to infections of all kinds.

"It suggests that [secondhand smoke] affects the infant's immune system in some way," said Dr. John Saito, an assistant professor of pediatrics at Texas A&M Health Science Center College of Medicine.

"The take-home message is that there is a distance factor here. If you are a certain distance away, it certainly reduces your child's risk," added Saito, who is chief of pediatric pulmonary, allergy and immunology and director of the Cystic Fibrosis Center at Scott & White Hospital, in Texas. "So while we have a very difficult time getting people to quit for a long period of time or at all, the message is that even if you can't manage to quit, just the fact that you can smoke outside or in the next room or just limiting the exposure significantly reduces the chance of your child getting an infection or being hospitalized, at least based on this study."

More information

The American Lung Association   has more on the effects of secondhand smoke on children.