This is a follow-up to Thinking Problems – Lab Leak. One could have thought that, by now, the issues of COVID would have faded into the background, but no. Misinformation about the COVID vaccine is still circulating.
In discussions with JP, there was a common claim that “they”
had said that the vaccine would prevent transmission. For example, in August 2021, JP was
housebound because he was worried about a local outbreak. I asked about his vaccine status and his
reply indicated that there would have been little consolation in having a
second jab if he could still spread it.
A month later he was claiming that the “initial focus was on preventing
spread”.
The problem is that the issue is very complicated. I know that I am going to overly simplify
things here, but I do so with the intent of getting past an apparent blockage
on the part of some of the more conspiracy minded among us.
For a virus-based disease, there is sequence of events somewhat like this:
When thought of like this, it is clear that having a vaccine
cannot help with certain stages. You are
either exposed or you are not. With
infection, that’s more a question of whether you ingested the virus or not. Here things are a bit blurry because there is
you and there are your cells. There is
also the virus and there are virions.
It’s possible that a virion (one particle of the virus) got into you,
but did not enter a cell (thus infecting it) before being excreted or
destroyed. Did you (the human) get
infected by the virus? You certainly got
closer than if you were merely exposed to the virus (ie sitting in a room in
which virions were floating around in the air that you breathed, but you didn’t
happen to breathe in one).
What about if one or a few of your cells did get infected,
but your immune system immediately identified the threat and destroyed the
infected cells before they could set up their virus replication process? You didn’t contract the disease, your body as
a whole didn’t get infected, but you were partially infected.
What about if you did get widespread infection of cells by
the virus, your immune system swung into gear mounting an effective response,
but you never got any symptoms – meaning that, strictly speaking, you never developed
the associated disease? This is
non-symptomatic infection, which in hindsight appears to have happened with
considerable frequency. Usually, being
non-symptomatic means you are not contagious.
But not always (as the Typhoid Mary case demonstrates).
I am going to just highlight a grey area between infection
by the virus and development (or contraction) of the disease. For the purposes of this argument, I am
counting disease as including the non-symptomatic who produce enough virions to
be contagious.
If viruses didn’t cause disease, we probably wouldn’t care
about them. It is worth noting though
that not all the symptoms of an infection are due to the pathogen (virus or
bacteria) per se – some of them are the immune system fighting against the
infection (fevers for example).
The job of a vaccine is to prepare the immune system for fighting
a specific pathogen (or suite of pathogens).
The better prepared the immune system is, the less likely it is that the
disease will take hold. This can range
from preventing symptoms entirely, making the symptoms less severe and reducing
the time that it takes for the immune system to eliminate the disease.
Viruses are particularly nasty because they take over the
cells of hosts and redeploy them to replicate virions. It’s rarely a friendly take-over, with the
replication machinery set to keep working until the cell bursts, releasing thousands
of virions which go on to infect new cells.
Quickly, the body is riddled with virions which then get into various
liquids in the body, including those in the lungs, meaning that when an
infected person breathes out, there are virions lurking in droplets that we
inevitably spread about us.
This is transmission in the schema above. The virus effectively uses us to spread
itself around us in a fog of about 1.5-2 metres (as is most visibly noticeable
on a cold day). But note that
transmission does not mean reception (exposure or infection).
If you have a viral disease, the only way to prevent transmission is to prevent droplets getting out and to another person. The right sort of mask, when worn properly, can do that. Or keeping away from others (social distancing). Or not going out in public (isolating). The vaccine will not help you, if you already have the disease. Your having been vaccinated will also not help you if it is not you who has the disease, it won't stop stop someone else transmitting.
What the vaccine will do is increase the likelihood, if you get virions into your body, that
your immune system will prevent an infection progressing to disease, reduce the
seriousness of the disease if you can't prevent it (and possibly reduce the number of virions you
produce that can then be transmitted to someone else) and shorten the period in which you have the
disease (and are contagious).
In that sense, the vaccine can certainly minimise spread of the
disease.
But it will never prevent contagious people from
transmitting the virus, nor will it necessarily prevent you developing some form of the
disease if you are infected (although it's much more likely to be mild, or even asymptomatic, rather than severe).
That’s not to say that there aren’t sterilising vaccines or
other treatments –that are hugely effective and prevent you from producing
virions if treated. It’s simply that the
covid vaccines were never advertised as those.
The effort was all about preventing severe disease, which is why they
are described as COVID-19 vaccines not SARS-CoV-2
vaccines.
