Vaccine vs. natural immunity

Have just seen a Twitter post by US Senator Rand Paul (Kentucky):

Firstly, Senator should be congratulated on doing correct math and comparing numbers (not a common feature among politicians, see below). There is a bit of a problem that we do not know whether either vaccine or natural immunity is lasting (and whether the 200 reinfections are a valid estimate, or represent initial values in a bigger wave resulting from loss of immunity), but there is also a deeper issue with these calculations.

And this is safety:

Naturally acquired COVID-19 immunity comes with significant side effects. Assuming 1% infection fatality ratio (IFR) which is a currently accepted value, COVID-19 leads to 1 in 100 serious side effects. In my medicine leaflet, this is listed under Common side effects. If a vaccine led to 1% deaths, it would not pass the regulations.

Without prejudging the safety of Pfizer and Moderna vaccines when they are widely rolled out, the current status is that the level of serious side effects is less than 1 in 10,000 which is classed as Very rare side effects.

I am not saying the vaccine is completely safe – we do not know this at this stage – but it appears much safer than the natural immunity.

I wish Senator was honest and not only mathematically competent.

Another example from today’s Twitter shows somebody who is neither honest nor mathematically competent.

Sadly, 50,000 divided by 5,000,000 is not 0.1% but 1%. I wish politicians:

  1. Knew how to do mental math, or at least knew how to use a calculator
  2. When the mistake is shown to them, they could say sorry and delete the tweet.


There has been quite a lot of excitement recently concerning the trials of COVID-19 vaccines. It remains to be seen when they will become widely available, whether they are as effective – as safe – as claimed. In the meantime, it is good to remind ourselves how the trials and their analysis are carried out.

My new article at The Conversation gives an overview of some numbers behind the vaccine trials and plans for the deployment. If you know Spanish, there is even a translation available!

To herd or not to herd

I was drafting a new post on herd immunity and the way to approach the second wave, but have just found the text of the John Snow Memorandum which does it much better than what I could do.

The Memorandum, currently signed by nearly 400 people, addresses the temptation to try to achieve “herd immunity” among young people, while protecting the “vulnerable”. This idea is not something very outlandish as shown by the Great Barrington Declaration as well as by signals from different governments:

“We heard strong reinforcement of the Trump Administration’s strategy of aggressively protecting the vulnerable while opening schools and the workplace,”

The John Snow Memorandum responds:

Any pandemic management strategy relying upon immunity from natural infections for COVID-19 is flawed. Uncontrolled transmission in younger people risks significant morbidity and mortality across the whole population. In addition to the human cost, this would impact the workforce as a whole and overwhelm the ability of healthcare systems to provide acute and routine care.

Moreover, the Memorandum gives a solution:

Once again, we face rapidly accelerating increase in COVID-19 cases across much of Europe, the USA, and many other countries across the world. It is critical to act decisively and urgently. Effective measures that suppress and control transmission need to be implemented widely, and they must be supported by financial and social programmes that encourage community responses and address the inequities that have been amplified by the pandemic.

Continuing restrictions will probably be required in the short term, to reduce transmission and fix ineffective pandemic response systems, in order to prevent future lockdowns. The purpose of these restrictions is to effectively suppress SARS-CoV-2 infections to low levels that allow rapid detection of localised outbreaks and rapid response through efficient and comprehensive find, test, trace, isolate, and support systems so life can return to near-normal without the need for generalised restrictions.

Protecting our economies is inextricably tied to controlling COVID-19. We must protect our workforce and avoid long-term uncertainty.

I could not agree more.

PS. A great thread on Twitter with a lot of number-crunching: