One dose of the swine flu vaccine is sufficient to induce an immune response in people aged six months and older, and pregnant women can safely be immunized with either of the licensed swine flu vaccines, the World Health Organization said Friday.
The highest-level advisory body to WHO on immunization and vaccination policy, an advisory group comprised of experts from around the world, has reviewed the results of clinical trials involving several thousand people and more than several hundred thousand who have been vaccinated in "real field" operations organized by 14 countries.
"All the reports received today following vaccination either in clinical trial or live vaccination campaign have showed the safety profile of these pandemic vaccines is good and is very similar to the ones which are known for seasonal influenza," Dr. Marie-Paule Kieny, director of WHO's Initiative for Vaccine Research told reporters during a briefing Friday from Geneva.
"Nothing special in terms of adverse events has been noted," Kieny said.
Given the significantly higher risk of severe complications in pregnant women who get infected with H1N1, especially in their second and third trimester of pregnancy, "these women can be vaccinated with any of the currently licensed vaccines," Kieny said.
She said both vaccines have a similar safety profile. "There is no reason, in (the vaccine advisory panel's) view, to distinguish between both types of vaccines."
The world body said a review of the current epidemiological situation of pandemic flu worldwide shows that teens and young adults continue to account for the majority of infections. Hospitalization rates are highest in the very young.
Between one per cent and 10 per cent of patients who get sick with H1N1 need to be hospitalized, and, of those who are hospitalized, 10 to 25 per cent need to be admitted to an intensive care unit; from two to nine per cent admitted to an ICU will die, WHO says.
About 10 per cent of all hospitalized patients are pregnant women in their second or third trimester, WHO says. And, pregnant women are 10 times more likely to be admitted to an ICU compared to the general population.
In July, WHO's vaccine advisory panel recommended pregnant women receive an non-adjuvanted vaccine if one was available. An adjuvant is a compound added to a vaccine to boost the immune response to the shots. That recommendation led Canada to order 1.8 million doses of non-adjuvanted vaccine for pregnant women — a regulatory decision that is now leading to vaccine delays that threaten to compromise the rollout of the largest immunization program in Canada's history.
The federal government said it was informed by Canada's H1N1 vaccine manufacturer, GlaxoSmithKline, that vaccine supply will be lower next week because its facility only has one production line for two types of vaccine.
GSK first produced batches of vaccine with an adjuvant, and by the end of the day Friday, six million doses will have been shipped to the provinces and territories. It temporarily switched its production line to manufacture 1.8 million doses of vaccine without the adjuvant, the vaccine that is preferred for pregnant women. It has now switched back to making the adjuvanted vaccine but because of the interruption caused by making the non-adjuvanted vaccine, there is reduced number of doses for next week.
That could lead to cancellations of clinics and further pressure on public health departments to get high risk groups immunized. Nationwide, Canadians are enduring hours-long waits for the shots while worried parents jam emergency room departments, looking for their children to get tested for H1N1.
The IWK Health Centre in Halifax has cancelled some elective surgeries for children and women, and some ambulatory clinics, as of Friday, to cope with the pressure H1N1 is putting on emergency and other areas of the hospital.
In Geneva, Kieny said more evidence has become available since the recommendation for pregnant women was made in July. Studies in animals using both adjuvanted and non-adjuvanted vaccines have found no evidence "of direct or indirect harmful effects on fertility, pregnancy, development of the embryo or fetus, birthing or post-natal development," WHO said in a statement.
After reviewing the evidence, the expert advisory panel, known as SAGE (Strategic Advisory Group of Experts), concluded "there is no reason to favour one vaccine as compared to the other for all these groups, and in particular for pregnant women," she said.
"These vaccines are very safe. There is nothing against giving a booster, certainly in terms of safety, but also in terms of scarcity of these vaccines right now, you can take the other option and say that the second dose could be used to vaccinate another person."
In countries where children age six months to 10 years old are on the priority list for receiving vaccines, the priority should be to give them at least one dose of the vaccine to cover as many as possible, Kieny said.
The WHO panel also said both the seasonal flu shot and H1N1 vaccine can be given at the same time.
The recommendation that pregnant women be vaccinated with either flu shot comes as a new review of data from three past flu pandemics and 11 studies on vaccine safety over 44 years found no increased risk of flu vaccine to mothers or their babies. Published in the American Journal of Obstetrics and Gynecology, the review confirms influenza puts pregnant women at greater risk for complications., such as pneumonia and severe respiratory distress that can lead to miscarriage or early delivery. Pregnancy decreases a woman's lung capacity and her heart works harder to supply blood to her and the baby.
In the first four months of the H1N1 outbreak, pregnant women were hospitalized at four times the rate of other healthy adults infected with the virus, according to the authors, and pregnant women made up 13 per cent of all H1N1 deaths during that period.
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