Re: Malaysia will get 200,000 H1N1 vaccines in January
Sunday January 10, 2010
H1N1 vaccination
By Dr MILTON LUM
For the vast majority, H1N1 is a flu like any other, in that it is self limiting. For a small segment ? those at risk of complications ? it is a flu like no other. Who do we vaccinate?
THERE have been several developments since the H1N1 pandemic was declared by the World Health Organisation (WHO) on June 11, 2009.
Data on its clinical features and those at risk of complications have been published and are still emerging. It is now known that between 1% and 10% of patients with clinical illness require hospitalisation. Globally, teenagers and young adults account for the majority of cases, with hospitalisation rates highest in very young children.
Of those hospitalised, between 10 to 25% require admission to an intensive care unit, and 2 to 9% die. Pregnant women infected by H1N1 are four to five times more likely to be hospitalised and up to 10 times more likely to need care in an intensive care unit when compared with the general population.
In short, H1N1 is a flu like any other for the vast majority, in that it is self limiting, but a flu like no other for a small segment of those infected, especially those with risk factors.
The number of deaths in Malaysia has remained at 77 since September 19, 2009. This compares with 190 deaths in Australia (James Bishop et al, NEJM, November 25, 2009).
The pandemic progressed to the second wave in autumn and winter in the northern hemisphere. Recent reports from the United States and Canada indicate that the second wave of the pandemic which started early in the autumn is beginning to ebb.
Although influenza transmission remains widespread, it has declined substantially in all countries. The indicators of severity in the United States, e.g. hospitalisations and mortality, have declined substantially since the peak in late October.
The situation in Europe is less clear. After a near doubling of mortality fortnightly since late October 2009, the mortality rate has decreased in western Europe. However, there is still active and widespread transmission in western Europe, but the overall disease activity has peaked. The most active areas of transmission are currently in central and eastern Europe. (WHO, December 30, 2009)
Transmission in East Asia, although active, appears to be declining. The same is the case in Malaysia.
The view from WHO is guarded. It?s director general, Dr Margaret Chan, stated on December 30, 2009, that the H1N1 virus is likely to continue circulating around the world for another year. ?I think it is too premature and too early for us to say we have come to an end of the pandemic influenza worldwide. It would be prudent and appropriate for WHO, together with our member States, to continue to monitor the evolution of this pandemic for the next six to 12 months,? she said.
Director General of WHO, Dr Margaret Chan, stated on Dec 30, 2009, that the H1N1 virus is likely to continue circulating around the world for another year. ? AFP
The economic costs of the pandemic are coming into print. Using data from 2004, modelling done by Smith RD et al (BMJ 2009;339;b4571) predicted a reduction of 0.5 to 4.3% in the United Kingdom?s (UK) gross domestic product (GDP) of between 0.5% and 4.3%, which is equivalent to reductions in UK output of between ?8.4 and ?72.3bil.
Vaccines against H1N1 have been developed by several pharmaceutical companies. Populations or population groups in developed and some developing countries are being vaccinated for health as well as economic reasons.
H1N1 vaccines
There are various H1N1 vaccines. They either contain live viruses that have been weakened in the laboratory (attenuated) or killed (inactivated) viruses, with and without adjuvants.
All the vaccines are based on the viral strain called A/California/7/2009 (H1N1)v. The vaccine manufacturers have adapted the manufacturing processes they use for the seasonal and bird flu vaccines. The vaccines differ in the conditions used for virus propagation, antigen preparation, and antigen content. The culture mediums used are vero cells or egg derived.
Adjuvants are substances that increase a vaccine?s potency. This leads to smaller amounts of virus antigen needed per person, thereby resulting in increased availability of vaccines to more people. The addition of adjuvants to the H1N1 vaccines has increased the vaccine production capacity of some manufacturers by 100 to 200%. Despite this increase, there is insufficient capacity to meet global needs. The adjuvants used in H1N1 vaccines are alum or squalene based. The former has been used in many vaccines for about 60 years and the latter, which is an extract of fish oil, in seasonal flu vaccines since 1997.
Thiomersal is commonly used in the manufacturing process of many vaccines. This ethyl mercury compound prevents the H1N1 vaccines in multi-dose vials from contamination by microorganisms. Thiomersal does not contain methyl mercury, which is a naturally-occurring compound whose toxic effects on humans are well known. Unlike methyl mercury, thiomersal does not accumulate, and is broken down and removed from the body much faster than methyl mercury.
Thiomersal?s safety has been studied extensively with no evidence of toxicity reported in infants, children or adults, including pregnant women, exposed to vaccines containing thiomersal.
The H1N1 vaccines are not expected to provide protection against other influenza viruses. As the current seasonal influenza vaccines do not contain the H1N1 virus, vaccination has to be given against both, when indicated. However, the situation could change in the future.
The H1N1 vaccine, like other influenza vaccines, is effective about 10 to 14 days after vaccination. People infected by H1N1 just before (one to three days) or after vaccination can still get the disease.
Administration
The inactivated vaccines are given by injection into the upper arm for most people. However, the thigh is preferred in infants and younger children. The live attenuated vaccine is administered by a nasal spray.
The recommendation for the number of doses of the vaccine for an immune response varies. The European Medicines Agency (EMEA) and the Centres for Disease Control (CDC) of the United States currently recommend two doses of the inactivated vaccine at least three weeks apart. However, the Chinese authorities suggested a single dose of their inactivated vaccine was sufficient to induce a typically protective immune response in the majority of subjects between 12 and 60 years of age (NEJM, Oct 21, 2009).
Reports have also emerged from other current clinical trials in China, Hungary, United States, and Australia. The preliminary results suggest that one dose of H1N1 vaccine will be adequate for healthy adults of all ages, while children aged below nine years may need two doses. However, the optimum use of a H1N1 vaccine remains an unanswered question (Lancet, Jan 2, 2010).
It is likely that, as more reports are published, the dosage recommendations may be adjusted for all or different specific age or other groups of the population.
Certain people cannot be given inactivated vaccines. They include:
?Those with a history of anaphylaxis or other life-threatening allergic reactions to any of the constituents of the vaccine.
?Those with history of a severe reaction to previous influenza vaccination.
?Those who developed Guillain-Barr? syndrome (GBS) within six weeks of getting an influenza vaccine.
?Those who are having fever (they should wait until they have recovered to get vaccinated).
?Infants less than six months of age.
Seasonal and H1N1 vaccines can be administered at the same time, if both vaccines are inactivated, or one is inactivated and the other is live attenuated. There is currently no evidence that the risk of adverse events is increased by simultaneous administration of these vaccines.
The CDC recommends that there should not be simultaneous administration of live attenuated seasonal and live attenuated H1N1 vaccines.
Inactivated H1N1 vaccine can be administered simultaneously as other injectable, non-influenza vaccines, but at different injection sites.
Effectiveness
Although there is no vaccine that provides 100% protection against a disease, vaccination reduces the risk of disease.
The objective of the current H1N1 vaccine strategy of two doses at least three weeks apart in many developed countries and a single dose in China is the achievement of rapid protective immunity in those who have not been infected. About 70% of H1N1 vaccine recipients reportedly developed immunity.
The long term response to the H1N1 vaccine is unknown and is being studied in clinical trials.
However, it should be noted that clinical trials of H5N1 (bird flu) and other influenza vaccines have reported that the antibody levels decline with time.
Safety
WHO experts, who have reviewed the various preliminary reports, found no indication of unusual adverse events. Some of these are well within the range of that of seasonal influenza vaccines, which have an excellent safety profile.
According to the US Vaccine Adverse Event Reporting System (VAERS), there were 82 adverse event reports per one million H1N1 vaccine doses distributed, compared with 47 reports per one million seasonal influenza vaccine doses distributed. There were no substantial differences between the H1N1 and seasonal influenza vaccines in the proportion or types of serious adverse events reported.
Studies to date do not report of harm to pregnant women or the foetus. As the risk for hospitalisation and severe illness is increased in infected pregnant women, they should be vaccinated provided there are no contra-indications, as the benefits of vaccination far outweigh the risks.
Despite the encouraging reports, the monitoring for adverse events is on-going. This is as it should be as there is much knowledge about H1N1 and its vaccines that are yet to emerge.
Side effects
The side effects depend on the type of vaccine, how it is administered, and the age of the vaccine recipient.
The common local reactions to
inactivated vaccines include soreness, swelling and redness at the injection site. Fever, aches in the muscles or joints or headache are less common. The symptoms are usually mild and lasts a day or two. Fever, aches and headaches are more frequent in children. The side effects do not usually require medical attention.
Allergic reactions like rapid swelling of deeper skin layers and tissues, asthma or a severe multisystem allergic reaction are rare.
The common reactions to
live vaccines, which are given through a nasal spray, include a ?running? nose and cough. A sore throat, low grade fever, irritability, headache and muscle aches are less common. Wheezing and vomiting may occur in children.
Who to vaccinate?
When there is a vast gap between the number of vaccine doses available and the number of people who require vaccination, health authorities have to make decisions on who are to be vaccinated. These are difficult decisions and have to take into account the priorities that have to be decided on.
The priorities for vaccination depend on its objectives. This was discussed succinctly by Meltzer et al in 2003, i.e.
● If the objective is maintaining the functioning of a country?s critical infrastructure, then vaccinating the required personnel will be a priority, i.e. health care staff
● If the objective is preventing the greatest number of deaths, then vaccinating groups at high risk of influenza-related mortality would be the first priority, i.e. people with underlying conditions (but severe cases have been reported in healthy young adults)
● If the objective is to reduce viral transmission within the community, then targeting children is a consideration, i.e. school age children depending on local patterns
The people who are at increased risk of H1N1 infections and its complications are:
● People of all ages with chronic underlying conditions i.e. diabetes, cardiovascular disease, chronic respiratory disease, including asthma, and other conditions that impair breathing and or chronic health problems like obesity and some physical handicaps;
● Pregnant women;
● Young children (especially those under two years of age).
The risk groups in children are slightly different, with more emphasis on neurodevelopmental handicaps and less on chronic medical conditions like diabetes and cardiovascular disease.
However, individuals who did not have any underlying conditions have also died from H1N1 or its complications.
When the first wave of the H1N1 pandemic hit Malaysia, the public sector initially managed the problem itself. Private medical practitioners and healthcare facilities were instructed to refer all patients with influenza-like illness to designated public sector hospitals. But the public sector could not cope with the number of cases that swamped its clinics and hospitals, some of whom were genuine and many others who came because of fear or even panic. This led to the inclusion of private medical practitioners and health facilities in the delivery of healthcare to people with influenza-like illness. The development was a situation which was, to say the least, less than desirable.
The recent media announcements that H1N1 vaccines will be given to public sector healthcare providers and pregnant women have lead to d?j? vu among many private medical practitioners and healthcare professionals.
How can private medical practitioners and healthcare professionals be expected to take care of patients when they do not have an opportunity of protecting themselves with vaccination? Are they not front-line staff at increased risk of infection? Does the H1N1 virus make a distinction between medical practitioners and healthcare professionals in the public and private sectors?
It is time that the turf mentality be replaced with an inclusive approach that utilises all the nation?s health care human resources for the benefit of patients.
Who gets priority?
H1N1 is a flu like any other flu, in that it is self limiting, for the vast majority, but a flu like no other flu for a small segment of those infected especially those with risk factors. The spread of the infection can be controlled by practising personal hygiene.
However, vaccines offer a cost effective means of protection of large segments of the population.
The problem lies in the vast insufficiency of vaccines to meet global needs leading to decisions in prioritisation of vaccination. The H1N1 virus cannot make a distinction between medical practitioners and healthcare professionals in the public sector from those in the private sector.
One can only wonder how vaccinating only medical practitioners and health are professionals in the public sector and the pregnant will impact on the country?s health care infrastructure.
● Dr Milton Lum is a member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.
http://thestar.com.my/health/story.asp?file=/2010/1/10/health/5430173&sec=health
