Getting Technical
Frequently , a desirable objective to achieve by communities and populations is what is termed ‘ herd immunity ’, the term now commonly used for indirect protection from an infectious disease that happens when immunity develops in a population either through vaccination or through previous infection .
Herd immunity arises when individuals who are not immune are in communities which contain high proportions of those who are immune and is only achieved by person-to-person transmission . Not all infectious diseases can produce herd immunity . For example , tetanus infections come from bacteria in the environment , not from other people .
The WHO supports achieving ' herd immunity ' through vaccination , not by allowing a disease to spread through a population , as this would result in unnecessary cases and deaths .
To combat Covid-19 causing the relatively new global pandemic , many vaccines are still in development phases although some have now progressed to early treatment rollout , having demonstrated safety and efficacy against the disease .
“ Rather than having to treat a disease after it occurs , vaccines prevent sickness in the first place .”
The proportion of the population that must be vaccinated against Covid-19 to begin inducing herd immunity is not yet known , but is an important area of research and will , no doubt , vary according to the community , the vaccine , the populations prioritised for vaccination , and other factors . All the ingredients of a vaccine play an important role in ensuring a vaccine is safe and effective . Typical ingredients are :
• Antigens : Killed or weakened forms of viruses or bacteria , which train our bodies to recognise and fight the disease when it occurs
• Adjuvants : Which help boost immune responses so that they help vaccines to work better .
• Preservatives : Which ensure a vaccine stays effective .
• Stabilisers : Which protect vaccines during storage and transportation .
Vaccine ingredients can look unfamiliar when they are listed on a label . However , many of the components used in vaccines occur naturally in the body , in the environment , and in the foods we eat .
All of the ingredients in vaccines – as well as the vaccines themselves – are thoroughly tested and monitored to ensure they are safe .
Vaccines currently need to be maintained at relatively low temperatures ranging between – 15 and - 80 ° C . Several commentators have pointed out that continually increasing demand for vaccines offers a “ key opportunity to create a new global cold chain , part of which could at least be used to transport other goods like agricultural produce ". RACA
www . hvacronline . co . za RACA Journal I April 2021 35