A significant new study by South African and German scientists has provided the first evidence globally that even three vaccine doses may not be sufficient to prevent infection with the Omicron variant of the SARS-CoV-2 virus.
The study, “Breakthrough infections with SARS-CoV-2 Omicron variant despite booster dose of mRNA vaccine", was published in the authoritative medical journal The Lancet this morning (Wednesday 19 January 2022).
Omicron is the most recent SARS-CoV-2 variant of concern to emerge. Its ability for immune evasion (to cause infection even in the presence of some degree of immunity) was predicted on the basis of its mutation pattern and has been confirmed by observations of an increased incidence of re- and breakthrough infections.
This has triggered calls to intensify vaccination programmes, including the provision of vaccine booster doses.
In this study by a group of scientists from Stellenbosch University (SU), Ludwig Maximilians University of Munich (Germany), and the Universities of the Western Cape and Cape Town, as well as the National Health Laboratory Service, seven German visitors to Cape Town were studied who had received three doses of vaccines yet were infected with the Omicron variant in late November 2021.
The group consisted of five women and two men, four of whom were working at different hospitals in Cape Town, while the others were on vacation. They were members of two unlinked social groups and participated in regular social life in Cape Town in compliance with applicable Covid-19 protocols.
All seven of them were fully vaccinated. Six had received two doses of the Pfizer vaccine and later a booster dose of Pfizer in five cases, and a booster dose of Moderna Spikevax in the other one. The seventh individual had received an initial dose of AstraZeneca, followed by a dose of Pfizer and later a Pfizer booster. All seven had high levels of specific antibodies.
During a marked increase in infections in the Western Cape, the visitors started to experience respiratory symptoms between 30 November and 2 December 2021 and were diagnosed with Covid-19. They were all infected with the Omicron variant.
According to the authors of the study, they were placed in domestic isolation and used a daily symptom diary to document the course of the disease over 21 days. All seven of them experienced mild or moderate symptoms (shortness of breath). Their blood oxygenation levels remained in the normal range and none of them required hospitalisation.
This study is the first in the world to report, and characterise, breakthrough infections with the Omicron variant in fully vaccinated individuals after receipt of vaccine booster doses.
Booster doses were administered between 21 and 37 weeks after the second vaccine doses, and breakthrough infections occurred 22 to 59 days thereafter.
This data confirms insufficient protection against Omicron infection even after receipt of a booster vaccine dose. The small number of cases in relatively young and otherwise healthy individuals studied notwithstanding, the authors emphasise that the mild to moderate symptoms experienced may suggest that boosted vaccination still provides good protection against severe disease caused by Omicron.
This important study, the pre-print version of which has been downloaded more than 15 000 times in about five weeks, was conceived in a fortuitous manner: The joint first author, one of the seven Germans experiencing breakthrough infections (Constanze Kuhlmann from the Division of Hand, Plastic and Aesthetic Surgery at the Ludwig Maximilians University of Munich), contacted the last author (Prof Wolfgang Preiser, Head of the Division of Medical Virology at SU's Faculty of Medicine and Health Sciences), whom she did not know personally but had seen being interviewed about the Omicron variant.
Preiser says at the time, South Africa had yet to introduce booster vaccinations. “The presence of this group of Germans in South Africa, when it became the first country to experience a pandemic wave driven by the Omicron variant, presented a unique opportunity to generate highly relevant and sorely needed information on the implications of the newly emerged variant for vaccination.
“Clinical studies usually take weeks if not longer to prepare. To commence a study from one moment to the next required a lot of resourcefulness, innovative thinking, and extremely quick action to organise patient recruitment, arrange for sample logistics, and perform laboratory testing," he adds.
“Louis Pasteur's motto 'chance favours the prepared mind' was once again proven correct: Only an established, tried and tested network of collaborating scientists at three different Capetonian universities, each specialising in a different aspect, made this study possible."
The study's findings support the need for updated vaccines to provide better protection against infection with the Omicron variant and emphasise that non-pharmaceutical measures should be maintained for now. Encouragingly, early data from South Africa subsequently suggested maintained, if reduced, effectiveness of the Pfizer vaccine against hospitalisation.
This study was approved by the Health Research Ethics Committees of SU and the University of Cape Town and all participants provided informed consent.
Caption: Prof Wolfgang Preiser
Photo credit: Damien Schumann