Menu Home

Covid Diary: Explaining Defence.

The Moral Dog’s Owner is a Doctor so the usual provisos that her Opinions are hers only do come tweaked with Medical Knowledge gleaned over three decades and a swine flu pandemic.

The Owner is expecting imminent Covid because of close contact. So apologies for hijacking the Moral Dog’s blog but:

How to defend ourselves against Covid

Covid is a new bug for mankind, and like most new bugs that affect us , it jumped to people from animals. Many human diseases jumped from animals, including measles, the bubonic plague, HIV, ebola, influenza and the common cold.

In the modern world we have four defences against new infections:

  1. Our Own immune systems. Number one in every way, these are brilliant as we have been developing them for hundreds of thousands of years. They are why we don’t die from every cold or infected insect bite. They have defended the world’s population, as a whole, against plagues and pestilence since long before we had antibiotics and science. They defend us, much of the time, against cancers. They consist of millions of cells primed to recognise pathogens, neutralise them and remember them for the future.
  2. Immunisation. This piggybacks onto number one. Immunisations merely give our own immune systems advance warning of what may be coming, so that we can prepare. Immunisation is probably medicine’s greatest gift to the world. It has nearly eradicated polio. It eradicated smallpox. It protects against measles, which I and my friends all had in the pre vaccine era (some of us died). It protects against rubella. It protects against meningococcal disease, which was something we all expected to see when I was a junior doctor and now see rarely in the UK. Immunisation is a fabulous public health advance. It is imperfect, as not all immunisations are 100% effective, but it also helps with herd immunity (see below). However for Covid-19 we don’t have a vaccine yet, and if we develop one it won’t be for some time. So we can’t bank on that yet, at least.
  3. Antibiotics and antivirals. These have saved us from many overwhelming bacterial illnesses and a few viral ones. We don’t have one fr Covid-19 yet, although the search is on, and again we can’t bank on it. We don’t have nearly the range of effective antivirals as we have antibacterials. But it is being worked on, as we need it for those whose immune systems can’t do the job themselves.
  4. Healthy Group Herd Immunity. Herd immunity means group immunity. It means that if most of a population are immune to a virus, the virus cannot circulate in the population, so those who are not immune to it won’t get it. As a population we use our immune systems to kill the virus so that those whose immune systems are not up to the job don’t need to. Healthy Group Herd immunity allows protection of the vulnerable by the immunity that the healthy majority acquire. A population acquires herd immunity either because they have been vaccinated or because they have had the infection. If we want to use Healthy Group Herd Immunity to protect the vulnerable, however, we cannot just let the virus sweep through us all. This approach only protects the vulnerable if the ‘herd’ who catch the infection are the healthy and strong ones. If 60% of all of us, across the board, young and old, have Covid then at least 1% will die. However, if the strongest 60% of us have Covid, the figure could be very very much lower than that. However, it will still not be zero. Some Healthy People do become sick, including critically sick, and need Critical Care. A very small proportion do die, even with the best care. For this reason Healthy Group Herd Immunity is not a perfect strategy. It would be better to have stopped the virus in its tracks. It would be better to have a vaccine, a treatment or, preferably both. It would be better if the virus had not come. But with the virus still spreading and no vaccine imminent, the best we can do is to slow it down, protect those most likely to die, and do the best we can to ensure that those least likely to die have access to the best the NHS can do.

So what does this mean for me and my Covid?

I am expecting to experience the Virus over the next 2 weeks. I do not regard myself as at risk as I am under 60 and fit, even though having just had surgery is not great. I am not afraid as, statistically, my risk of needing to go to hospital is low, but I know it could happen. After I have had the virus I should be immune to it. I will then be part of the Immune group, effectively a buffer of Protection for those whose Immune Systems are not as good as mine. And as an immune doctor, I’ll be useful as I can’t pass Covid to my patients.

If I weren’t already almost certainly infected, would I hide?

For my own sake, no. As a low risk individual who treats patients it is better to have had it, if I can have it safely. At the time of writing it appears that I can. I would like to be in the group that becomes immune, not the group that is only safe because others are immune, for my own sake too, so that the virus will not make me hide away again. For a doctor this has obvious extra advantages.

For the sake of this community, however, it is still better to delay acquiring it, because it would be better for our population that the virus spreads at medium speed through April and May than at fast speed through March. This would mean that :

  1. the numbers affected at any one time was less, even though the outbreak lasted longer.
  2. we won’t all be off work at once.
  3. the numbers needing hospital at any one time will be less.
  4. we may know more about possible treatments
  5. the outbreak would be in the spring and summer, when our NHS acute beds are not so full.
  6. it seems likely that we can protect the vulnerable more successfully if systems are not overwhelmed
  7. we will have enough intensive care beds for the critically ill

Why is everyone so frightened?

Older people, whom we love, are at risk. Front line medical staff, who may get a very high level of exposure to multiple patients with the virus, may have worse infections. So we need to protect them.

The best way to do that seems to be by a massive community effort to contain the virus as far as we can, and allowing only those in the healthy group to expose themselves to it by doing essential work. It looks as if the virus will still spread, but we may have some control over where it spreads, and how fast it gets there.

If we do this then there is a good chance that those who have had it will be permanently immune, and those who are not immune but would be at risk won’t have it. The best method we have to stop the pandemic is ourselves.


I have had Covid. It was mild for a week and moderate for a few days. It is now resolved. The Covid diary is here. It proved nothing to be afraid of in a 58 year old who is normally healthy but who, as it happened, had fairly major surgery around the day she caught it.

Don’t be afraid. Our job is to look out for each other, to be socially responsible, to work together and to save the people we can save. For some of us that is going to mean having Covid. Please don’t panic. Only a small percentage of the normally well will need a doctor. And if you do, we will be there for you.

Categories: coronavirus Covid-19

Hergest the Hound

I am a dog of many thoughts.

7 replies

  1. Nuna commented that she heard you can get COVID twice. Of course IF you could get it twice, in quick succession, AND it was just as bad second time round then herd immunity would not help the population. But this does not appear to be the case so far..
    There is no evidence to date of second infections, which suggests either it doesn’t happen, or doesn’t happen in the vast majority, and it certainly would not be typical of the way viruses and immunity behave.
    Whilst immunity might not be totally lifelong, if it lasts years as you would typically expect then herd immunity would still be good enough for many years. And if immunity were gradually lost in several years time then, because the loss would be at different times in different people, there would not be a whole world population of non immune people as there is now.
    For example I still have antibodies to measles which I caught 49 years ago.
    For now, the experts are telling us that, it looks as though one infection will give you immunity, assuming you have a normal immune system. This should reassure us.


  2. My one concern is for my elderly in-laws, trying to keep them safe does worry me as they fall into the demographic at greatest risk. Otherwise I think having to isolate if infected would have benefits, I could use the peace and quite and I have a considerable pile of books to keep me engaged.
    I assume in the UK you have to isolate if infected, so I hope Hergest won’t get too bored with any enforced time indoors. We have considered what we will do to keep our own delinquent hound amused if we can’t attend the dog park.
    Hope you don’t feel too bad if you develop the infection. A good time to re-read some Pratchett! Wishing you a speedy recovery.


  3. Thankyou! I have suggested to elderly parents who are vulnerable that they do start to self isolate soon if not now. Mine are not in London but in a rural area and there are few cases where they are yet, but if their strategy is to be avoiding the virus then this seems sensible now, particularly if it is easy for them. Means we can’t visit, but we can phone. And Facetime.

    Liked by 1 person

  4. The Owner notes, for completeness, that if the virus could have been shut down and held at bay, and a vaccine could have been developed in the time thus bought, that would of course have been better. But the virus was never contained, from its point of arrival in humans. It escaped China and so its local containment may prove of little benefit since it will return. There is no choice but to have a significant proportion of the population have the virus now. What we can still hope to do is to control how quickly, and who we shield from it.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: