Wednesday May 20, 2009
Value of vaccination in fight against diseases
Stories by WONG LI ZA
The importance of vaccination is irrefutable, particularly in the fight against infectious diseases.
NEW parents are all too familiar with the frequent clinic visits for their baby’s vaccinations. In the first two years of a child’s life, he or she will receive at least 10 mandatory vaccinations against various diseases like Hib (Haemophilus Influenzae type B), Hepatitis B and poliomyelitis as part of the national immunisation programme.
However, vaccinations do not stop at childhood; common adult vaccinations include flu, Hepatitis A and B, and pneumococcal vaccines.
Vital: Vaccines are one of the most valuable ways to protect people during influenza epidemics and pandemics, with other measures being anti-viral drugs, social distancing and personal hygiene. The most severe influenza pandemic in the 20th century was the Spanish flu (1918-1919), estimated to have killed about 50 million people worldwide. In recent years, the world faced new threats in the forms of the 1997 H5N1 bird flu and Severe Acute Respiratory Syndrome (SARS), and now, the influenza A (H1N1) near pandemic.
According to the World Health Organisation (WHO), as of May 18, 40 countries have officially reported 8,829 cases of influenza A (H1N1) infections, with 74 deaths. At press time, the WHO pandemic alert is at Phase 5. This phase is characterised by human-to-human spread of the virus into at least two countries in one region and is a strong signal that a pandemic is imminent. Should the alert be raised to Phase 6, that would mean the H1N1 virus has spread worldwide and there is sustained human-to-human transmission.
“The H1N1 is a new virus and so very few people are immune or have the antibody to fight it,” said Prof Dr Arthur Reingold, head of the Epidemiology Division, School of Public Health, University of California.
He said the annual seasonal influenza in the United States is also serious and kills about 40,000 to 50,000 people a year. “How-ever, the current H1N1 virus may not necessarily cause the same number of deaths,” said Reingold via a video conference with Malaysian and Singaporean media last week.
A recent study published in the Journal of Infectious Diseases found that influenza A virus infection in conjunction with bacterial infection led to most of the deaths in the 1918 Spanish Flu pandemic. The study, carried out by the US National Institute of Allergy and Infectious Diseases postulated that the majority of deaths likely resulted directly from secondary bacterial pneumonia caused by common upper respiratory-tract bacteria.
“Pneumonia affects the very young and very old. Some are primary infections from the virus itself but most will be affected by secondary bacterial infections.
“There is no data yet on whether that will happen in this current epidemic but from anecdotal evidence, some of the patients did develop bacterial pneumonia,” said Reingold.
Therefore, the use of bacterial vaccines to control the current epidemic will not be unreasonable and will depend on how many people actually experience bacterial pneumonia, or lung infection, he added.
What then are the roles of influenza antiviral drugs and influenza vaccines in controlling a pandemic?
Reingold that said with annual flu epidemics, experts project what type of virus will cause the seasonal flu and then develop the vaccines accordingly. However, such vaccines are not expected to give protection against the current H1N1 virus.
“With the H1N1, we do not know what causes it or how it is going to evolve in the next 12 to 18 months. Until a few weeks ago, when the H1N1 first came about, everybody thought that bird flu virus would be the next pandemic strain in people.
“Flu viruses can change very quickly, so this new virus may become harmless and disappear, continue at the same severity, or become even more deadly,” he portended.
At the moment, medical experts are in the process of developing a vaccine for H1N1 which is expected to be ready by September or October.
“Once it’s ready, the next question is how much can be produced and how soon. Each adult will probably need two doses of the vaccine and with six billion people worldwide, that means it may take four years to develop the 12 billion doses,” he explained.
In light of that, strategic use of the vaccine will be crucial in minimising the spread of the disease and ensure basic societal needs are met.
Reingold said that one way of controlling the spread of pneumococcal infections (a complication caused by influenza) is to vaccinate young children. “Infants have high rates of pneumococcal infections. By vaccinating young kids with pneumococcal conjugate vaccine, we will also prevent the spread of pneumococcal disease to their siblings, parents and grandparents,” he said.
In 2006, WHO recommended that countries with substantial pneumococcal diseases should introduce pneumococcal vaccine into young children’s vaccination programmes.
“Giving adults and infants pneumococcal vaccine is a good form of preventing influenza pandemics,” said Reingold, who chairs an advisory expert group within WHO on pneumococcal vaccines.
Basic practices like covering one’s mouth when sneezing, staying at home when feeling unwell and washing one’s hands are equally important measures to prevent the spread, he said.
“These are on top of using Tamiflu (oseltamivir) antivirals to treat those already infected,” he said.
Antivirals, Reingold added, should also be given to frontline healthcare workers and emergency response personnel as a preventive measure, but not to be administered to the general population.
In painting a silver lining, Reingold stressed that most people who contracted the Influenza A virus recovered without antiviral treatment, unlike the H5N1 bird flu which killed 60% of the people infected.
WHO states that vaccines are one of the most valuable ways to protect people during influenza epidemics and pandemics, with other measures being anti-viral drugs, social distancing and personal hygiene.
Influenza vaccines generally contain a dead or weakened form of a circulating virus. The vaccine prepares the body’s immune system to defend against a true infection. For the vaccine to protect as well as possible, the virus in it should match the circulating “wild-type” virus relatively closely. Since this H1N1 virus is new, there is no vaccine currently available made with this particular virus.
Early signs of Influenza A (H1N1) are flu-like and includes fever, cough, headache, muscle and joint pain, sore throat, runny nose and sometimes vomiting or diarrhoea. The outbreak occurs via human-to-human transmission. When infected people cough or sneeze, infected droplets get on their hands, drop onto surfaces, or are dispersed into the air. Another person who breathes in the contaminated air or touch infected surfaces will be exposed.
Antiviral drugs may reduce the symptoms and duration of illness, just as they do for seasonal influenza. They also contribute to preventing severe disease and death. However, they do carry some side effects like vomiting, diarrhoea and dizziness.
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