{UAH} How vaccines work

By Misaki Wayengera

How vaccines work, and why even after you are vaccinated you need to protect yourself in the context of the small numbers of vaccinated people in Uganda?

I am driven to write this post, in response to many misinforming media coverage regarding the ability of the AstraZeneca vaccine used in Uganda, to protect against COVID19 and its variants.

First, I want to assure Ugandans that the SOUTH Africans ( and that's their prerogative) prematurely dismissed  the AstraZeneca ( ASZ) vaccine.  Their study aimed to study the ability of vaccine to protect against infection and NOT severe disease.  From what we now know the ASZ vaccine protects against severe disease ( and hence death ) caused by the Delta variant to the same extent as Pfizer ( 33.7 % at 1st dose and upto 51.1% at 2nd dose). 

Vaccines work in two ways, 1st to protect against infection ( achieved communally when many people in society are vaccinated ) and 2nd protect against severe disease and death ( this is the most important benefit at personal level).

That said....what does the data on vaccine efficacy mean in literal terms, if we say 1st dose protects upto 60% and 2nd dose to 92%. It means in 100 people vaccinated against COVID19 by ASZ, only 62 will be protected by 1st dose and upto 92 will be by 2nd dose. It implies that even at 2nd dose some 8 people might randomly get infected ( and possibly even get severe disease and die). The numbers protected are less with only one dose.

Does that mean vaccine doesnt work? Of course the answer is a big NO.  It simply means if you want to maximize protection by vaccination you need to vaccinate more people to attain herd immunity. Herd immunity provides a compounding of the protective effects of the vaccine. This is why when we want to eradicate polio or measles we do mass vaccinations. It's also why India stopped its exports and zeroed on vaccinating more people, to attain a threshold number of people needed to offer a communal shield against transmission and infection. Generally, we know that vaccinated people even when they get infected have lower viral loads and therefore transmit less. 

Finally, it's important to know that it takes about 2 to 4 weeks ( average 21 days) for the 2nd jab of the vaccine to achieve maximum efficiency. Myself ( among the 1st people to get my 2nd dose, by virtue of my leadership role and not priviledge) just made 4 weeks this week. Thus,  very many people in Uganda have  still not reached maximum protection. That is why it is important that, even among those who have recieved a jab or two, we continue to wear masks and protect ourselves for atleast a month. Moreover, in context of the communal benefits of vaccination, one can only say they are safe not to wear masks if over 65 to 85% of the population is fully vaccinated. This is what we see our colleagues in the west attempt to do, return to normalcy after vaccinating a threshold number of their populations. 

#StaySafeUG

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