Annual vaccination has been recommended by the World Health Organization as the most effective solution to combat seasonal influenzas like swine flu, which has to date killed more than 1,200 this year alone in India.
"It is recommended that people get a flu vaccine even during seasons when drifted viruses are circulating. It's because vaccination can prevent some infections and can reduce serious ailments that can lead to hospitalisation and death," stated the Geneva-based health agency.
The Indian health ministry had declared a few days ago that vaccination was necessary only for health care workers.
The trivalent influenza vaccine gives protection against H1N1, H3N2 and Influenza B. The vaccine takes at least two weeks to develop immunity and provides about 60-80% protection for about a year.
Some of these influenza viruses may circulate later in the season, the WHO said in its report.
A recent drop in temperature from a weather anomaly in many parts of India has resulted in delaying the onset of summer and further increased spread of swine flu.
The health organisation has noted with concern that the present season has seen widespread and severe influenza in many parts of the world mainly because of an antigenic drift or mismatch between the strain used in the vaccine and that found in the community.
In fact, Public Health England had declared that as few as 3% of winter flu vaccines this season have been effective.
The genomes of influenza viruses (A, B and C) are made of eight separate RNA segments that can be shuffled in various permutations and combinations when a bird or mammal is co-infected with different viruses.
Formation of a new viral type by small changes in individual RNA segments is called antigenic shift.
However, these small genetic changes can accumulate over time to produce enough minor changes that cumulatively alter the virus' makeup over time.
With 18 HA (haemagluttinin) and 11 NA (neuraminidase) subtypes known, influenza viruses can are constantly reinventing themselves to stay a step ahead of vaccines and drugs.
This is happening now at an accelerated pace.
As a consequence, the flu vaccines have fared poorly than in previous years.
Symptoms and drugs
The WHO has asked healthcare providers and workers to ensure that all persons with symptoms of respiratory infection adhere to respiratory hygiene when visiting clinics.
Physicians should watch out for emergency warning signs that require immediate attention like difficulty in breathing or shortness of breath, chest pain, coughing coloured sputum, severe or persistent vomiting, altered level of consciousness and confusion.
The health agency had recently warned that the world could see pandemics worse than the 2009 swine flu outbreak that killed over 280,000 people.
Two antiviral agents have been reported to help prevent or reduce the effects of swine flu. They are zanamivir (Relenza) and oseltamivir (Tamiflu), but these drugs should not be used indiscriminately, because viral resistance to them can and has occurred.
Also, they are not recommended if the flu symptoms already have been present for 48 hours or more.
Last year, the FDA approved the first new anti-influenza drug in 15 years, peramivir injection (Rapivab). But the drug induces side-effects in some including diarrhea, skin infections, hallucinations, and/or altered behaviour.