Business Times - 16 May 2009
Double your protection
Besides going for a flu jab during an outbreak of influenza, , it could be just as important to get inoculated against bacterial infection. By Cheah Ui-Hoon
WHEN there's a flu virus going around, one's first thought is to get a flu jab to get some kind of protection against the disease. But what could be equally important is to get inoculated against bacterial infection, now that a recent study has shown that the majority of deaths during the Spanish flu pandemic (1918-1919) resulted from secondary bacterial pneumonia.
'Experts now believe that if adults and infants are vaccinated against pneumococcus, it's a good form of preparedness for influenza epidemics,' says Arthur Reingold, head of the epidemiology division of the School of Public Health in the University of California, Berkeley, in a video conference earlier this week.
A recent study conducted by the National Institute of Allergy and Infectious Diseases in Maryland in the US has shown that the influenza A virus infection, in conjunction with bacterial infection, led to most of the deaths in the 1918-1919 pandemic which resulted in more than 50 million deaths worldwide.
There is no formal stand on this by the World Health Organisation, Prof Reingold clarifies, but adds that experts like him believe that getting inoculated against bacterial infections would be a reasonable thing to do in advance of a flu pandemic.
As it is, vaccinations against bacterial infections like streptococcus pneumoniae (or pneumococcus) and haemophilus influenza B are routinely administered already. 'Countries have been recommending or using the infant pneumococcal vaccine since 2000, and the haemophilus influenza B infant vaccine since the 1990s,' he points out.
But their importance in a flu pandemic is increasingly being looked at by experts, he adds. Infants, for example, have a high rate of pneumococcal infections and they are a primary spreader of the disease to their siblings, parents and grandparents.
As for the current swine flu which has so far claimed at least 49 lives worldwide, with 29 countries having official cases numbering over 4,300, Prof Reingold says that a vaccine should be developed by September or October this year at the earliest.
But even then, it will take four years, going by current production capacity, to manufacture enough vaccines for the world's population of six billion, he adds.
The current understanding now is that the vaccine for this new influenza A (H1N1) infection will have to be given in double doses, so pharmaceutical companies need to produce 12 billion doses to cover the world's population if there's a decision to vaccinate against this strain. This, of course, may not happen if the strain doesn't end up being very virulent.
However, there are a lot of unknowns about this virus currently, says Prof Reingold. Scientists aren't even sure how it will evolve in another season.
It is considered a pandemic now because it is widely distributed, but it is too soon to know how lethal it is. At present, it seems quite possible that its lethalness will be on par with that of the strains that cause annual epidemics. 'Annual influenza kills 40,000 to 50,000 people a year in the US,' he points out.
Until a few weeks ago, in fact, scientists were preparing for a bird flu (H5N1) pandemic. Since the outbreak of bird flu in Hong Kong in 1997, the world has seen the virus spread throughout the world in birds, resulting in a 50 per cent fatality rate among humans who contract it.
'So the World Health Organisation is in the process of building up a repository of 150 million doses against the H5N1 virus in case there's a pandemic,' he says.
As for the swine flu, the worry is that no one knows how it will mutate in 12 to 18 months' time. 'The virus is under great pressure to evolve and change quickly. It could disappear or continue at the same level of severity, or it could become more lethal,' he says. 'What we do know is that it's readily transmissible and already all over the world,' he adds.
The wearing of masks if you're coughing or sneezing is the paramount means of preventing the swine flu from spreading, he notes - even more so than temperature screening. In fact, he points out that post-outbreak studies of measures taken in Canada - such as getting travellers to fill out cards and temperature screenings at airports during the Sars outbreak - showed that they failed to reduce its spread. 'It picked up those with fevers, but none of those people had Sars. Those who did get Sars weren't picked up during temperature screening,' he says.
In fact, people infected with this present influenza A flu virus are shedding the virus in their respiratory tract before they develop symptoms, and are infectious to others as soon as they begin to cough and sneeze. Sars, on the other hand, was transmissible only after a person got quite ill. 'So there's very little evidence that screening travellers will work,' Prof Reingold says, adding, however, that he can't fault public health officials for setting up some form of vigilance.
Pneumococcal vaccines available here
IN SINGAPORE, there are currently two pneumococcal vaccines available commercially here. The heptavalent pneumococcal conjugate vaccine is marketed for children but is not on the national immunisation programme's list of vaccines. Hsu Li Yang, consultant, division of infectious diseases, university medicine cluster of the National University Hospital, says that he understands from surveys that the uptake for this vaccination is between 15 and 20 per cent.
The adult 23-valent vaccine and haemophilus influenza B vaccine are also not on the national immunisation programme's list of vaccines, and it is not known what the rate of uptake is. But Dr Hsu would certainly recommend that adults who fall into the known risk groups for severe pneumococcal disease and children be vaccinated. This includes adults who are above 60 years old; and children below two years old, who are immuno-compromised due to chronic illness, or who are undergoing chemotherapy or radiotherapy.
'Patients with severe influenza infection can get a bacterial superinfection of the lungs - usually with staphylococcus aureus (there is no vaccine for this) and streptococcus pneumonia, and die from that,' says Dr Hsu. This is the main cause of death in the majority of flu pandemics as well as seasonal influenza.
Patients may also get a viral pneumonia with accompanying 'cytokine storm' - that is, an exaggerated immune system response to the infection - and die as a consequence. This was believed to be the primary cause of the flu-related deaths during the Spanish flu outbreak in 1918-1919, and is the primary cause of death for avian (H5N1) influenza as well.