Does a report from the German public health agency Robert Koch Institute (RKI) show that 95% of those infected with the omicron variant of the SARS-CoV-2 virus are vaccinated? No, that's not true: This calculation is based on incomplete data published in a weekly report by RKI on December 30, 2021, that included vaccination status for only about half the patients thought to have been infected with the omicron variant in Germany. That alone makes calculation of vaccine effectiveness impossible.
But the report also contained an error that has since been corrected: The number of infections among the unvaccinated had not been updated in the report template from a previous version, listing 186 when the correct tally was 1,097. In some articles that used the RKI report to claim vaccines are not effective against the omicron variant, the percentage of vaccinated patients among infection cases has since been updated to 78.6%. This is, however, still based on incomplete data and does not take into account that the vaccination status of 51% of omicron cases is unknown. At the time this fact check was written, the RKI did not offer reliable data on how well the COVID-19 vaccines protect against the omicron variant.
The claim appeared in an article (archived here) by The Gateway Pundit on December 30, 2021, under the title "Germany: 96% of Latest Omicron Patients were FULLY Vaccinated - Only 4% Unvaccinated." It opened:
A new study in Germany of 4,206 Coronavirus patients found that 4,020 were fully vaccinated individuals.
186 of the Coronavirus patients were unvaccinated.
At the time of writing, users on social media saw this headline:
(Source: thegatewaypundit.com screenshot taken Tue Jan 4 18:56:02 2022 UTC)
RKI report is preliminary
The article is based on data from the RKI weekly report on COVID-19 in Germany on December 30, 2021. These weekly reports contain preliminary data only and users are cautioned not to draw conclusions on vaccine efficacy from them. For the omicron variant, the report contains the following data on page 14 (translated from German by this reporter):
Between November 21, 2021 and December 27, 2021, a total of 10,443 (suspected) cases of the Omicron variant were reported via the IfSG reporting system in Germany (data status December 28, 2021), of which 1,555 were confirmed beyond a doubt via genome sequencing, while 8,888 were classified as suspected cases via variant-specific PCR testing.
RKI report was missing vaccination status for half of omicron cases
On page 14, the report specifies clinical and epidemiological data for some of those 10,443 cases. In 6,788 cases, additional information on symptoms was included. Most of those patients reported no or only mild symptoms. According to the report, vaccination status was unknown for 51% of the cases where the omicron variant was detected. Of the 5,117 cases for which the vaccination status was known, 4,020 were fully vaccinated and of those, 1,137 had received a third dose.
First version of RKI report contained erroneously low number of unvaccinated patients with omicron -- about 1/6th the correct tally
When the RKI report was first published, the number of unvaccinated patients infected with the omicron variant was given as 186, the same number as the previous weekly report from December 23, 2021 (page 38). In an email to Lead Stories on January 3, 2022, a spokesperson for the RKI confirmed that this was simply an oversight and that the authors of the report used a prior report as a template and neglected to update the number. This error was corrected on January 3, 2022, and now gives the number of unvaccinated patients as 1,097.
The headline of the Gateway Pundit article, which claims that 96% of those infected with the omicron variant were vaccinated, is thus based on a false number.
An article by The National Pulse, published on December 31, 2021, had originally also claimed that over 95% of omicron cases occurred in the vaccinated. This article was updated on January 4, 2022, with a new calculation based on the updated numbers in the RKI report.
The author of the article still claims, however, that nearly 80% of omicron cases are in vaccinated people, which does not reflect the data in the report correctly. Among omicron cases, vaccination status was unknown for 51%, 38.5% were vaccinated and 10.5% were unvaccinated. In an email, a spokesperson for the RKI confirmed that they did not have any estimates yet on how the omicron variant affected vaccine efficacy.
Claims that both the erroneous and the corrected numbers show that infections with the omicron variant were more likely in the vaccinated also leave out other important context, such as the fact that the higher the vaccination rate in a given population, the higher the percentage of infected persons who have been vaccinated. The absolute number of cases may be small while the percent is glaringly large.
In an FAQ on the RKI's website, the reasons for increasing breakthrough infections with a higher vaccination rates are explained as follows, translated from German
That a higher vaccination rate leads to more breakthrough infections is to be expected. ... This does not indicate that the vaccines do not work but can be explained based on the following aspects.
(1) The efficacy of the COVID-19 vaccines is very good, but not at 100%. This means: even though the vaccines are very effective, they cannot prevent all infections in the vaccinated. They do, however, ensure that infections happen less frequently and that severe cases of COVID-19 become very rare in those fully vaccinated.
(2) When the vaccination rate increases, the likelihood increases that there are infection cases among the vaccinated population. This means: when the share of the vaccinated increases in the population, the likelihood that among those that are infected or become ill include vaccinated patients also increases. Simply put, if everyone in a population is vaccinated (vaccination rate of 100%), the rate of breakthrough infections within those that become ill is also at 100% (with a vaccine that is less than 100% effective.)
(3) Additionally, the number of breakthrough infections also depends on the number of active cases. The more active cases there are, the higher the likelihood to become infected as a vaccinated person. This means: if the virus is not, or hardly is, present in the population, the likelihood for an infection, and thus for a vaccine breakthrough, decreases. Simply put: if there is no virus circulating, there are no breakthrough infections.
A high number of active cases and a relatively high vaccination rate can thus lead to an increasing number of breakthrough cases. This also increases the probability that those people that are hospitalized with a SARS-CoV-2 infection also include vaccinated patients. But even an increasing number of vaccinated patients among hospitalized COVID patients does not mean, that the vaccines are not effective. Rather, the total number of hospitalized cases is lower the higher the vaccination rate is.
Lead Stories has explained this effect in other contexts before, most recently here and here.
The latest weekly report that contained data on vaccination rates was published by the RKI on December 23, 2021. Up to December 22, 73.6% of the German population had received one dose of a COVID vaccine and 70.5% were fully vaccinated with two doses. In addition, 33.8% had received a third dose.
