How protected am I after one dose of vaccination?

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More than 3 million Austrians have already received the first dose of a Covid 19 vaccine. But does the one dose already protect? A British scientist has compiled data from various studies and makes a clear statement for all four vaccines approved in the EU.

According to his data, even the first dose of vaccine provides a high level of protection against the coronavirus. Countries such as the United Kingdom are therefore extending the period between the two shots to guarantee initial protection for as many people as possible. For “Business Insider,” Stephen Evans has summarized how much protection the first vaccination offers in percentage terms with BioNTech, Moderna, AstraZeneca and Johnson & Johnson. He is a professor of medical statistics at the London School of Hygiene & Tropical Medicine (LSHTM) and a former member of the European Medicines Agency’s Committee on Safety of Medicines.

What exactly does percentage protection actually mean?
BioNTech/Pfizer

According to U.S. Food & Drug Administration (FDA) documents, the protection of the first BioNTech/Pfizer vaccine dose is 52.4 percent. However, this period includes the first eleven days after the prick. Immune protection does not kick in until around day 12. The actual protection of the first vaccine dose is said to range from 29.5 to 84.5 percent. That’s a pretty wide range. However, it is not possible to make a more precise statement, since hardly any people fell ill with corona during the series of investigations.

Nevertheless, there is good news: the active ingredient is said to provide 100 percent protection against a very severe course – i.e. a stay in hospital or a fatal outcome – already after the first injection. During the test series, only four patients suffered a severe Covid 19 disease – all four were part of the placebo group and therefore not vaccinated with the active substance developed in Germany and the USA.

The expert’s conclusion: Professor Stephen Evans says there is “very clear evidence” that the first dose of vaccine provides at least 80 percent protection, more likely 90 percent.

Moderna
As with BioNTech/Pfizer, the protection provided by the first Moderna vaccine dose can only be roughly estimated: between 43.5 and 84.5 percent. The reason again is that few people contracted Covid-19 during the testing period. Specifically, it is stated that the first shot should protect about 69.5 percent, but again this includes the days before the onset of immune protection.

During the Moderna trial, seven percent of subjects did not receive a second dose for unknown reasons. These people had 50.8 percent protection 14 days after their first and only prick. After two weeks, this rose to 92.1 percent. It is difficult to assess how effective the U.S. agent is against severe courses, he said. During the test phase, only four participants in the placebo group and two vaccinated individuals became severely ill.

The expert’s conclusion is that Evans estimates that the efficacy of the first dose of Moderna is also at least 80 percent, more likely over 90 percent.

AstraZeneca
AstraZeneca’s active ingredient has come under criticism several times in recent months because of isolated cases of thrombosis. In Germany and some other countries, vaccination with the active ingredient has been discontinued in the meantime. While countries such as Denmark have now dispensed with it altogether, it is still used in Germany, but is only recommended for patients over the age of 60. Professor Evans admits in an interview with Business Insider that it is difficult for AstraZeneca to quantify efficacy. The reason for this, he says, is different research designs of the test series. In addition, he says, the FDA has not yet presented the results of the test phases in as much detail as it has for the other vaccines.

However, according to a March 2021 study, a single dose of the Swedish-British active ingredient is expected to provide 76 percent protection – for at least 90 days. In addition, protection against a severe course would be 100 percent. However, as with the two vaccines mentioned above, the number of people infected was very small. Thus, no generally valid statement can be made.

The expert’s conclusion: based on previously published studies, Professor Evans estimates that the first dose of AstraZeneca vaccine provides more than 70 percent protection for at least 90 days.

Johnson & Johnson
Unlike the BioNTech/Pfizer, AstraZeneca and Moderna agents, the Johnson & Johnson vaccine consists of only one dose. However, that is not the only difference. While the competition focused on symptomatic corona disease in their test series, Johnson & Johnson focused on moderate to severe courses.

With this vaccine, too, protection does not kick in until about 14 days. After that, the U.S. vaccine is said to be 66.1 percent effective. However, there are said to be differences here depending on the country. While it was 72 percent effective in its home country, only 64 percent protection was demonstrated in South Africa and 68 percent in Brazil. This trend could be due to the virus variants that are strongly represented in both countries.

What exactly does percentage protection actually mean?
Vaccine efficacy is always expressed as a percentage. This value indicates the percentage of people who are fully protected after vaccination. So if, for example, Johnson & Johnson in South Africa put the efficacy at 64 percent, that means 64 percent of people were fully protected and 36 percent were not.

Those who have already developed full protection from the first dose of vaccine will get a better and longer-lasting immune response from the second shot. Those who are not yet fully protected can develop that protection through the second dose. However, this is not always possible. Some people cannot be protected even by a complete vaccination because their immune system does not respond.

sources: One Shot of COVID Vaccine: Here’s How Much Protection You Get (businessinsider.com)/AstraZeneca trotz Gefahr von Thrombose wieder im Einsatz- FITBOOK/Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials – The Lancet/picture: pixabay.com

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