Advantages & Disadvantages of Inactivated Vaccines

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Inactivated vaccines are composed of dead viruses and bacteria, allowing for a safe method of immunising against these pathogens as they can’t behave as they normally do and cause disease. Despite their inactivated state, these pathogens still possess the identifying molecules that signal their presence to the immune system, which means that we still receive the benefits of being immunised against that particular condition. In this article we look at the advantages and disadvantages of using inactivated vaccines.

What are the advantages of inactivated vaccines?

Inactivated vaccines can provide a high level of protection against disease if the dosing and booster regime is followed. Top up doses are needed, as will be discussed in more detail later in this article, but if they are taken as advised then the immunity offered by inactivated vaccines is of a very high standard.

One of the risks of live attenuated vaccination is the possibility of reversion, and this isn’t an issue with inactivated vaccines. Live vaccines contain living viruses and bacteria that have been treated in such a way that they are no longer virulent or a threat to human health. One of the concerns in their use however is that they may undergo changes in their genetic code (mutations) that would lead to their return to a dangerous wild form of the disease. This is called reversion, and because inactivated vaccines are dead, there is no risk of any change that could pose a threat to human health.

Because dead pathogens do not actively attack the human body, inactivated vaccines can be provided to people suffering from immunity issues. Such people are referred to as ‘immunocompromised’, which simply means that their ability to defend themselves against infection has been diminished. Examples of immunocompromised populations are people suffering from HIV, a virus which directly attacks the immune system, or cancer patients receiving chemo- or radiotherapy, both of which damage the immune system and suppress it. These people are particularly vulnerable to pathogens, which is why even attenuated vaccines can pose a risk.

Inactivated vaccines are also particularly in practical terms as they can be freeze dried for ease of transport. Live vaccinations need to be stored at low temperatures to remain viable, and this poses an obstacle when it comes to the transport and supply of vaccines across long distances and to parts of the world where adequate storage facilities can be lacking. Conversely inactivated vaccines are far more convenient for shipping and storage purposes, a major advantage both for manufacturers and aid groups seeking to transport large quantities of vaccine across the world.

What are the disadvantages of inactivated vaccines?

While there are many advantages to their use, there are some distinct disadvantages to inactivated vaccines which are an important consideration when choosing which method of vaccination is best suited to purpose.

Some inactivated vaccines are less effective than their live counterparts, and while a live vaccine triggers an immune response so strong that usually a single dose is enough to immunise a person, inactivated vaccines need regular booster injections. This is not only inconvenient and sometimes unpleasant where multiple injections are needed, but poses a real practical problem for travellers and in areas where the healthcare system is not established enough to conduct regular and routine vaccination for its resident population.

One of the issues with inactivated vaccines is that they don’t effectively stimulate an element of the immune response called local or mucosal immunity. This is, however, stimulated by live vaccines. Mucosal immunity is an important front line defence that deals with a lot of pathogens before they make their way into general circulation. A great example of a key element of the mucosal immune response is an antibody called immunoglobulin A, which is found in mucosal lining of the respiratory tract and prevents a lot of infections around the lungs an throat.

Inactivated vaccines can sometimes be quite expensive because of the treatment processes involved in inactivating a vaccine. This is obviously a major concern when it comes to large scale immunisation programmes where millions of doses are needed.

Finally there has been an incident where the inactivation procedure has failed to safely render a virus harmless. This case involved the accidental administration of virulent smallpox, a severe condition. Since this event greater care is taken in ensuring that all the pathogens contained within a vaccine have been effectively eliminated.

With all these points in mind it is important to remember that the benefits of inactivated vaccination outweigh the disadvantages to the point where their widespread usage is commonplace across the world. Inactivated vaccines are an important part of the immunisation programme.

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