Vaccination is highly protective against Covid-19

As in Europe, the US is currently experiencing a surge in Covid-19 cases and hospitalizations driven by transmission among the unvaccinated.  Two days ago, health officials in Vermont noted that 90% of Covid cases in Intensive Care Units are unvaccinated. Currently 74% of the Vermont population is fully vaccinated. This information allows us to do a simple calculation using only high school algebra to estimate the difference in risk of severe Covid infection among vaccinated compared to unvaccinated.

Let us say the infection rate among the unvaccinated is I and the relative risk of severe infection in vaccinated versus unvaccinated is R. So the infection rate among the vaccinated is R*I.

Let us assume a population of 100 in which 74 are vaccinated and 26 are unvaccinated. Then the number of severe infections requiring admission to ICU is 26*I unvaccinated and  74*R*I vaccinated. So the proportion of ICU cases who are unvaccinated is 26*I /( 26* I + 74 *R*I), and we know that this ratio is 0.9. So we can write:

                26*I / ( 26* I + 74 *R*I)  = 0.9    

Solving this equation for R:

                                        26* I       =  0.9 * (26*I + 74 *R*I)  

or                                         26      =  23.4  +  66.6*R

so                                      R       =   (26-23.4)/66.6    = 0.039

Thus the vaccinated have a risk of severe Covid infection that is 3.9% of that for the unvaccinated.  Inverting this, we can say that the unvaccinated have 1/0.039  = 25.6 times the risk of severe infection as the vaccinated.  The actual risk will vary somewhat in populations with the mix of Covid variants and the overall time since vaccination, but the figures from Vermont graphically illustrate the huge protection that full vaccination provides.  And the evidence is that this protection is definitely enhanced by getting a third booster shot.

A previous post I made on the importance of boosters attracted a couple of anti-vax comments claiming ^ that I was admitting the vaccine did not prevent Covid. I hope the simple analysis above of readily accessible data is adequate to clarify to anyone who thinks like this that the vaccine offers a huge level of risk reduction. And if you were vaccinated more than five or six months ago, get a booster! It improves the level of protection further.

Booster shots and the current Covid-19 Delta wave

Switzerland is now offering a covid19 booster shot to to the 65+ and at-risk who has had their two covid19 vaccinations at least six months ago. It may soon be extended to all adults. I had my third shot last Thursday with no side effects (not even a localized sore spot) and was surprised to receive a Pfizer booster after being fully vaccinated earlier this year with the Moderna vaccine. The mRNA in both vaccines encode the same S-2P protein which differs from the covid19 spike protein by two amino acids only. These stabilize the spike protein so that it can train the immune system before it enters the host cell. I’ve been reading up on booster shots and will try to provide a brief summary below. If you want citations and more detail on the studies, see my professional blog here.

A large study of 1.14 million Israeli adults, aged 60 years and over who had received two Pfizer doses at least 5 months earlier, found that a third shot reduces the risk of infection by the dominant Delta variant by a factor of 11 compared to fully vaccinated people who have had two shots.  Receiving a different vaccine type as I did, further reduces the risk by around 30% or more. The booster shot lowers the risk of severe illness even more, by a factor of around 20 compared to those who have had two shots only.

Israel was the first country in the world to make available a third dose of the Pfizer vaccine to everyone aged 60 and over who had been vaccinated at least 5 months earlier. Since then, Israel has extended the booster program to the entire population. Booster doses per 100 people rose from zero at the end of July to over 40 per 100 currently.

Israel had a huge spike in infections this summer due to the combination of the highly infectious Delta strain, together with waning immunity in fully vaccinated people. Its clear from the following graph that the booster shots were definitely a game changer.  There was a very steep reduction in infections, hospitalizations and deaths among the people that got the booster shot. Israel went from over 11,000 new cases a day at the peak, down to a few dozen today. Before the booster campaign started hospitalizations were rising among vaccinated people whose immunity had waned, but the overwhelming majority of hospitalizations now are of people who are unvaccinated. During this period the fully vaccinated rate was fairly stable at a little above 60% of the population.

The same combination of waning immunity and Delta are now causing rising cases in Europe, as illiustrated in the following plot. Austria, Belgium and the Netherlands are currently the hardest hit (see graph below), with average daily new cases well over 1,000 per million, higher than any previous wave. In most of the countries on this graph, fully vaccinated rates are somewhere between 60 and 75%. That means around 25 to 40 percent of these populations are unvaccinated and their much higher susceptibility to infection is driving the latest surge in Delta infections.

Germany, Austria and the German-speaking region of Switzerland have the largest shares of unvaccinated populations in all of Western Europe. About one in four people over 12 is unvaccinated, compared with about one in 10 in France and Italy, and almost none in Portugal.

Governments are struggling to address this shortfall in vaccination levels. Austria has introduced a lockdown for anyone over the age of 12 who is not vaccinated and foreshadowed compulsory vaccination for all adults. Germany is considering new restrictions and in Saxony the unvaccinated are already barred from non-essential shops and other locations. The Netherlands has flagged that they will move to full lockdown for the unvaccinated but not the vaccinated. Switzerland has a referendum next weekend on whether to continue with the vaccine mandate which allows only fully vaccinated people to go to theatres, restaurants, gyms and other indoor public venues.

There were violent anti-lockdown protests in Netherlands a couple of days ago. Police in Rotterdam opened fire on the crowd and shot three protesters, after firing warning shots in the air. Can we continue to let such people cause wave after wave of infections, causing not only disabiliinty and preventable deaths in the vaccinated also, but limiting work, education and life opportunities for those doing the right thing and getting vaccinated?

Some commentators have raised the moral issue of whether it is just for people in countries like Switzerland to get booster shots, when the large majority of people in many developing countries still have no access to vaccination. Despite the best efforts of WHO to get the developed countries to provide funding for the purchase of vaccines for poor countries, there has been little response.

I totally support that initiative and would certainly vote for politicians who would make sure Switzerland steps up to help fund such efforts. However, if I did not accept a booster shot it is not going to get sent to a developing country so I see my duty to the community is to step up and have the booster to help end the current Delta wave in Europe. Perhaps there should be a popular initiative to force the Swiss government to provide more aid funding for vaccinations, rather than the one we will vote on next week, put up by anti-vax people to try to block action to safeguard us from further Covid waves and lockdowns.