The Delta variant of the coronavirus broke through the protection of no fewer than three different vaccines at one meeting. American researchers describe this in a scientific article that appeared on the preprint server medRxiv. The observation again makes it clear that although vaccines against corona largely protect people against serious disease, there is still a risk.
The meeting in early April involved a wedding near Houston, Texas. Six of the 92 wedding guests became infected, even though the party took place outside in a marquee and all attendees were fully vaccinated with Pfizer-BioNTech, Moderna or Covaxin.
The outbreak probably started with a man and a woman who traveled to the party from India. Both had received their second dose of the Indian vaccine Covaxin ten days earlier. Perhaps that was just a little too recently – on average it takes up to two weeks after the last injection before maximum immunity is built up.
Prior to their flight to the US, the man and woman were still negative in a mandatory PCR test. On the first night of the wedding, the couple’s wife felt tired. She blames the jet lag and diabetes, but when her husband started coughing two days later and she developed a fever, they decided to get tested again. Now both were positive. The man eventually died in hospital, the woman recovered.
Of the four other guests who became infected, one also ended up in hospital. He recovered with a course of monoclonal antibodies (Regeneron).
All infected persons said afterwards that they did not keep their distance from the couple from India. It involved two men in their sixties who had been vaccinated with Pfizer and two women in their early fifties who had received Moderna.
All four had received their last shot in January, first author Tim Farinholt of the Baylor College of Medicine in Houston emails back when asked. None of these patients had previously experienced any problems with vaccinations, so doctors assume their immunity should have been up to scratch during the wedding.
The incident in Texas shows that vaccine protection is not foolproof against Covid-19. Vaccination can in most cases prevent people from becoming seriously ill, but it does not completely remove that risk. And the highly contagious Delta variant nibbles a bit off that.
That certainly applies to Covaxin, which appears to be slightly less effective than most Western vaccines. Earlier this month reported manufacturer Bharat Biotech based on a large comparative study that Covaxin is 78 percent effective against Covid-19. However, that drops to 65 percent when the Delta variant is in play. Still worth it, but less effective.
At Pfizer saw Public Health England rather the same pattern: 93 percent protection against disease by the Alpha variant, but with the Delta variant this decreases to 88 percent. That’s still decent protection, but it does mean that vaccinated people should be aware that they can still get infected and pass the infection on to others if they don’t keep their distance.
Most corona infections in the Netherlands are now due to the Delta variant, which appears to be much more contagious than previous variants.
From Israel, where two-thirds of the population has been vaccinated with the Pfizer-BioNTech vaccine, come messages now that the effectiveness of the vaccine is much lower than expected due to the emergence of the delta variant: only 63 percent. Those conclusions from an epidemiological report by the Ministry of Health are still disputed by experts. In Israel there are still large groups that have not been vaccinated, for example the Orthodox Jews, which has made it difficult to contain the circulation of the virus.
A version of this article also appeared in NRC in the morning of July 7, 2021