Why We Need to Get a Flu Shot Every Year

Waaiz Alam Saad
Freshman
School of Life Sciences
Independent University, Bangladesh

April 13th, 2017

Influenza, which is often referred to as the "flu", is a viral respiratory disease which can cause severe complications and can even lead to death. Every year the influenza outbreak can seriously affect the population. The threat is especially high for children younger than 2 years, adults aged 50 years or older, pregnant women and also people with medical conditions.  The virus has the ability to spread rapidly between workplaces, homes, businesses and schools. Infection can result from inhalation of infected air, direct contact or by coming in contact with contaminated objects.

According to WHO, influenza occurs globally with an annual strike rate estimated at 5%-10% in adults and 20%-30% in children. Therefore, the best method to reduce chances of getting infected is to get vaccinated annually. The vaccine is a biological preparation which contains a dead or weakened strain of a pathogen or its toxin. The body produces defensive proteins called antibodies, which recognize and kill pathogens based on antigens (unique proteins or other molecules) found on or within the pathogen. The body retains memory of the pathogen, and is able to produce antibodies against the actual live pathogen if or when it is encountered.

Mortality from seasonal influenza and pneumonia, a common secondary infection from the flu, 2010-14. CDC

Each year, new vaccines need to be developed for influenza because these viruses are continuously changing and evolving. There are proteins on the surface of the virus called hemagglutinin (HA) and neuraminidase (NA). Our immune system identifies these proteins that are on the viral surface, and generates and produces antibodies against these proteins. The structures of the viral proteins are determined by genes. The genetic code of influenza changes or mutates frequently as it is very prone to copying errors when the viruses reproduce. If, for instance, there is a change in the gene encoding the HA protein, HA might change shape, and then antibodies that normally bind to the previous version of HA will no longer be able to. This would allow the newly mutated virus to evade the immune system. Mistakes or mutations occur randomly, so these changes occur slowly over time in a process known as antigenic drift. The consequence of this is that the virus eventually evolves resistance to any antibody that is common in a population.

Finding the ideal vaccine formula is therefore difficult. Vaccines are developed after careful surveillance and prediction of which strains will be common, and be likely to have an adverse impact, in the next year. Since the virus mutates rapidly, the effectiveness of vaccines can vary; they have been shown to decrease the danger of flu by about 50% to 60% among the overall population during times when most current flu viruses are same as the vaccine viruses. That may not seem like a lot, but if large percentage of the general population is protected by the vaccine, vulnerable individuals are less likely to come into intact with infected individuals. Vaccination therefore protects not only the vaccinated individual, but also others in the population; this is known as herd immunity. This is especially important for individuals who are at higher risk of acquiring severe flu, such as children, the aged, and people with certain chronic health conditions.

Saad is a Freshman at the School of Life Sciences. He plans to work in drug and vaccine development, and towards the improvement of diagnostic tools for infectious diseases.

Revisiting the 2009 Swine Flu Pandemic

Amira Mohammed Ali
Senior
School of Life Sciences
Independent University, Bangladesh

23rd March, 2017

Influenza, commonly known as the "flu", is a disease caused by the influenza virus. The virus is known for its ability to cause pandemics, in which cases of the disease spread across multiple continent. The 1918 Spanish flu pandemic is estimated to have killed up to 50 million people. The virus has resulted in a few more pandemics since then, notably the 1957 pandemic that claimed around 4 million lives worldwide, and most recently the 2009 swine flu pandemic. Influenza virus has several subtypes, and is known to frequently produce new strains. It not only also has the ability to adapt through mutations or random changes in its genetic code, but can also exchange genes with other strains of influenza in cases where two or more strains infect the same individual. Seasonal influenza is very common and occurs every winter throughout the globe, and the new strains we see every year occur mostly as a result of accumulating mutations. The other mechanism of variation, in which exchange of genes can create new, unpredictable strains, resulted in the 2009 H1N1 pandemic strain which had never infected humans before. It was derived from an animal influenza strain, and different from the seasonal H1N1 strains that normally affect humans.

The first infection with this new strain is believed to have occurred in March 2009 in Mexico. Immediately after the first case, suddenly a number of these new H1N1 infection cases were rushed into many clinics across the country. The outbreak received increasing attention as the infection started to spread out to the northern parts of America. The CDC (Center for Disease Control) collected patient samples from infected people, and confirmed the emergence of the new strain. After few weeks of initial emergence of the new virus, it spread to 74 countries causing 29000 cases. The WHO (World Health Organization) declared it a global pandemic. The number of infected patients increased steeply as the winter approached globally.

Intensity map of confirmed cases of 2009 swine-derived H1N1 influenza. Public domain

To tackle the infection, a huge number of antiviral drugs, Oseltamivir and Zanamivir, were released to treat the patients. When existing drug supplies were insufficient and sometimes ineffective in meeting the rapidly increasing demand for treatment, the FDA (Food and Drug Administration) issued emergency use of previously unapproved antivirals and diagnostic tests for the H1N1 strain. Other measures were taken at that time to halt the spread, e.g. by monitoring airports.

After these efforts, the pandemic started to decline from May 2010 and in August 2010, the WHO declared that it was over. Even though the pandemic was over, it had taken more than 18,000 lives (laboratory confirmed) and made many more people sick globally. The WHO then declared a post-pandemic period where people received help to overcome the difficulties they had gone through. To help prevent any such pandemic in the future, the US government and private manufacturers have developed a vaccine in the form of injections (flu shots) and nasal spray, for swine-derived H1N1 influenza virus.

Amira is a wanderer and tries to understand the wonders of life. She wishes to have a lab of her own one day where she will unravel the mystery of life.