The H1N1 influenza as reported by WHO on June 15 has reported 41,762 cases of infected persons of which there were 181 deaths. In Jamaica there are 11 reported cases and no deaths. This is the first pandemic to be declared in almost 40 years the WHO reported on June 11 and the race has begun for a vaccine now that a suitable strain sample has been sent to drug makers around the world.
Figure 1 H1N1 Influenza outbreak concentrations - http://www.healthmap.org/swineflu
On June 15, Baxter International said it finished tests on the A/H1N1 flu strain and is working on a vaccine that could be commercially available next month. Instead of the traditional method involving chicken eggs, Baxter is using its Vero cell technology to produce the vaccine much faster. Chicken eggs - huh? Let's start from the beginning.
What is the Flu?
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses), that affects birds and mammals. The name influenza comes from the Italian influenza, meaning 'influence'. The most common symptoms of the disease are chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. Once the virus enters the body, it begins the process or reproducing itself. The reproduction of viruses in the body involves six steps starting with the attachment of the virus to a host cell in the body. The virus then enters the cell and sheds its coat to release its DNA material for replication in the cell. Finally, once full with new virus cells the host cell will most times rupture and release the newly created virus cells in the body.
Figure 2 http://www.proteanservices.com/2009/05/06/how-viruses-reproduce/
Treatments Available
The fact that it is caused by a virus means that there are only two possible treatments:
1. Antiviral drugs - are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses. Unlike antibiotics, however, antiviral drugs do not destroy their target pathogen, they only inhibit their development.
2. Vaccines - a biological preparation that improves immunity to a particular disease. A vaccine typically contains a small amount of an agent that resembles a microorganism. The agent stimulates the body's immune system to recognise the agent as foreign, destroy it, and 'remember' it, so that the immune system can more easily recognise and destroy any of these micro-organisms that it later encounters.
While there are antiviral drugs available oseltamivir, the generic name of Tamiflu tablets, and Relenza, a spray made by GlaxoSmithKline, the focus has been on obtaining a vaccination, because mutations in the genetic profile of the virus may cause a resistance to antiviral drugs over a period of time.
How Vaccines Are Produced
A dose of vaccine may contain: a suspending fluid to carry the vaccine into the body, preservatives and stabilisers so the vaccine can be stored safely, and an adjuvant to improve the body's immune response. Vaccine manufacture starts by generating the very organism that produces the disease, the virus. Many bacteria, for example, can be grown on agar gel (tissue culture) but viruses are mass produced by infecting cells grown in tissue culture, one such cell that is used is a fertilised chicken egg. Then the pathogen must be altered to make sure it doesn't trigger the disease itself. This can be done by:
Weakening the virus by growing it repeatedly to select a strain which doesn't cause complications of the natural disease.
Extracting the part of the virus DNA that causes the immune response and using this in the vaccine. This involves the use of genetic engineering as the DNA or RNA sequence that triggers the symptoms of the body's reaction are removed and reproduced.
Killing the virus by heating it or by using a preservative.
The treated virus can then be combined with the other component stabilisers and immune stimulators to produce a dose of vaccine. Scientists are trying to find new ways of producing vaccines, particularly using biotechnology and genetic engineering.
This is only the first step as every drug that is developed has to be put through a series of safety tests. Before a vaccine is put into general use it has to be licensed and in order to be granted a licence the manufacturers have to demonstrate its quality, safety, and efficacy in preventing the particular disease that it is intended for, through tests and clinical trials of the vaccine.
Clinical trials involve four key phases:
Phase one - Safety
These initial trials are done on a small number of healthy adult volunteers (about 10-12 people).
Phase two - Safety and immune response
With the information from Phase one, the vaccine is then tested on several hundred people from the age group for which the vaccine is intended, e.g. elderly people, babies or older children.
Phase three - Safety, immune response and efficacy
This phase uses thousands of volunteers of the relevant age group. Its purpose is to show that the vaccine works safely in preventing the disease for which it is intended and has minimal side effects.
Phase four - Post-licensing evaluation
Even after a vaccine has been introduced, there is on-going surveillance to pick up any very rare side effects.
How Vaccines Work
When a person is exposed to a disease-causing pathogen, the immune system attempts to mount a defense against it and when it has destroyed it successfully, immunity results. When the defense is not successful, the result is disease and its consequences. In the process of developing immunity, the body produces substances known as antibodies against a specific pathogen and creates a 'memory' of this experience that can be called upon for protection, when needed, many months or years later.
The next time the person encounters that foreign body, the antibodies that circulate in the bloodstream work to prevent it from causing the disease, and eliminate it from the body. A vaccine works in a similar way. However, instead of suffering the natural infection, a vaccine creates a similar immune protection response without the disease. It engages the immune system to create immunity and forces it to prepare to fight off an infection whenever it is encountered, and as such the severity of the disease is reduced or has no effect at all on the body.
While the world awaits the relief from the production and distribution of vaccines, remember to practice safe handling and contact techniques. Remember to sanitise often.
- V.H.