Get a flu shot now to protect against winter infectionUpdated: Oct 26, 2019, 20:01 IST
The flu season has begun in India, with doctors reporting a steady increase in the number of people with symptoms of fever, headache, runny nose, cough and muscle pain over the last week. Most people having mild disease recover within a week with non-prescription medicines for fever and pain, but can lead to hospitalisation and death for people over the age of 65 years and those with a pre-existing risk developing life-threatening complications.
Seasonal influenza, including H1N1, infects 3 to 5 million people worldwide and kills between 290,000 and 650,000 each year, estimates the World Health Organization (WHO).
The flu strains causing a majority of infections change from year to year, so the WHO recommends a vaccine before the start of winter in the northern and the southern hemispheres to protect populations against infection, hospitalisation and death.
Since it takes about two weeks after vaccination to develop immunity against the flu viruses, people who haven’t got vaccinated in India this year must get their shots now.
“I recommend the flu vaccine for all high-risk groups, which includes people over 65 years, people with cardiopulmonary problems, people with chronic kidney diseases, heart disease..... all these people are at higher risk for influenza,” said Dr Randeep Guleria, director and professor of pulmonary medicine, All India Institute of Medical Sciences, who is a member of the WHO’s Scientific Advisory Group of Experts on influenza vaccination for emerging markets.
The big four
The World Health Organisation’s WHO Global Influenza Surveillance and Response System (GISRS)’s projections show the four influenza strains that will cause infection in 2019-2020 are A/Brisbane (H1N1)-like virus; A/South Australia (H3N2)-like virus; B/Washington (Victoria lineage) virus; and B/Phuket (B/Yamagata lineage) virus.
Of the four strains causing infection, India just tests for H1N1, which has infected 27,992 and 1,198 deaths till October 20 across states. This is almost double the 15,266 cases in 2018, when there were 1,128 recorded flu-related deaths, according to data from the Integrated Disease Surveillance Programme, ministry of health and family welfare.
Rajasthan is the worst hit, with 5,090 cases and 208 deaths, followed by Gujarat (4,840 cases, 151 deaths), Delhi (3,613 cases, 31 deaths), Maharashtra (2,259 cases and 239 deaths) and Uttar Pradesh (2,082 cases, 34 deaths).
The GISRS recommends a new seasonal flu vaccine twice a year against viruses projected to cause most illnesses during the upcoming season. For 2019-2020, it has recommended a quadrivalent vaccine against all four strains, and a trivalent that protects against three excluding B/Phuket (B/Yamagata lineage) virus.
The WHO’s updated winter vaccine recommendation for the northern hemisphere has two changes from its February recommendations: A/Kansas (H3N2)-like virus has been replaced with an A/South Australia (H3N2)-like virus; and B/Colorado virus being replaced with B/Washington virus, to reflect the changes in the circulating flu strains.
Unlike in the US and Europe, where seasonal flu cases rise in winter, India records two peaks of the infection, in winter and during monsoon.
“Disease surveillance over the last few years showed that tropical countries like India have a different flu pattern than the temperate regions. In the US and Europe, you get a huge number of flu cases only during the winter months; there is hardly any cases in summer. But in tropical countries, influenza causes infection throughout the year with two main peaks, one is in winter and one in the monsoon months, when here is a lot of humidly and rain,” said Dr Guleria.
“The pre-winter vaccine used to come classically in India as a northern hemisphere vaccine in October and November, so we recommended to the Drugs Controller General of India that India should have both the northern and the southern hemisphere vaccine. Now India has two vaccines, one in October (northern hemisphere vaccine), and the other in March and April, which is the one given in the southern hemisphere ahead of winter in, say, South Africa or Australia,” he said.
He recommends people to get an annual flu shot and follow the cycle each year. “I tell patients coming in October to get the winter vaccine now and take it pre-winter every year. And in May or June, I tell patients to the southern hemisphere vaccine every year in May or June. There is a slight difference in the flu stains circulating in the northern and southern hemispheres, but since we don’t have a tropical vaccine, this is the best policy,” Dr Guleria.
“Vaccination against flu is particularly important for people over 65 years, pregnant women, those with low immunity, chronic infections and pre-existing diseases, such as diabetes or heart, lung or kidney diseases, who are at a high risk of developing life-threatening complications,” Dr Anil Prasad, former professor and head of respiratory virology at V Patel Chest Institute, Delhi, and chairman of Influenza Foundation of India.
“The protection provided by flu vaccination can vary depending, in part, on the health and age of the persons getting vaccinated, but vaccination reduces the severity of illness, shortens hospitalisation duration, lowers intensive care unit (ICU) and death from flu-related complications,” said Prasad.