Scientists working at the University of Washington Medical School (UW Medicine), Washington, USA, have shown that either a third (booster) vaccination or infection with SARS-CoV-2 gives comparable magnitude and breadth of protection, but those who have been vaccinated twice but still get a breakthrough infection usually do not have a severe infection.
Of course, anyone who is unfortunate enough to get a breakthrough infection or who is unvaccinated, runs a far higher risk of serious illness and long-term complications than those who have all three vaccinations, so the case for vaccination remains unarguable. The news release from UW Medicine explains:
A recent study looked at the strength, durability and breadth of neutralizing antibody responses generated by breakthrough infections in individuals vaccinated against SARS-CoV2.The same study also showed that vaccines and infections by SARS-CoV-2 also gives moderate protection against SARS-CoV, the virus that caused the SARS outbreak a few years ago, but they do not protect against the coronaviruses that cause the common cold. This suggests that there may be future SARS-CoV-2 viruses with spike proteins that are not recognised by antibodies produced by the vaccines or infection with the current variants of SARS-CoV-2, highlighting the need to develop broader spectrum vaccines.
The findings are published this week in Cell, one of the scientific journals of Cell Press. Alexandra Walls and David Veesler in the Department of Biochemistry at the University of Washington in Seattle led the project.
Characteristics of the Delta and Omicron coronavirus variants of concern include enhanced transmissibility and immune evasion even in non-immunologically naïve individuals, compared to the ancestral pandemic coronavirus.
These characteristics, and the waning of immunity from vaccines, have led to breakthrough infections in vaccinated individuals. For the most part, otherwise healthy people who are vaccinated against the SARS-CoV-2 usually do not have severe symptoms if they do end up contracting the virus.
The researchers wanted to understand what effect catching the virus after being vaccinated has on neutralizing antibodies, and to see how durable and broad these responses are. Their hope is that advancing such knowledge will help guide vaccination policies and pandemic mitigation strategies.
Through their project the researchers learned that the degree of antibody response depended on whether a person has had one, two, three, or four exposures to the spike protein through infection, vaccination, or a mixture of the two. The scientists also checked antibody responses in groups of individuals who had been vaccinated after having COVID-19, those who were previously vaccinated and experienced a breakthrough infection, those who were vaccinated only, and those who were boosted and therefore vaccinated three times.
Among their study subjects, those who had completed a three-vaccination protocol, and those who had been vaccinated after recovering from COVID-19, and those with a breakthrough infection after vaccination launched almost comparable neutralizing antibody responses, in terms of magnitude and breadth. Their serum binding and antibody neutralizing responses to the spike protein in the current pandemic coronavirus variants were much more potent and lasting than those generated by people who had received only two doses of COVID-19 vaccine or who had a previous infection not followed by vaccination.
This observation suggested that the increased number of exposures to SARS-CoV-2 antigens, either through infection and vaccination or triple vaccination, enhanced the quality of antibody responses.
The researchers also looked at how broad the elicited antibodies could be. They investigated neutralization of the divergent Omicron SARS-CoV-2 variant of concern, currently responsible for the majority of cases in the United States. Their findings showed that boosted individuals (or those that have a mixture of infection and double vaccination) have neutralizing antibodies at similar levels to subjects vaccinated twice against the original ancestral strain. This suggests a large amount of immune evasion, but that vaccine boosters can help close the neutralizing antibody gap caused by Omicron.
Sadly, the published findings in Cell are behind a paywall, despite the journals professed support for open access publishing. However, the abstract can be read here. In it, the authors give the following highlights:
The conclusion should be obvious to anyone capable of thinking through the logic of these findings:
- Breakthrough infections induce potent neutralizing antibody responses
- Number of exposures (infection or vaccination) correlate with potency and breadth
- Three-dose vaccination improves neutralization of the SARS-CoV-2 Omicron variant
- SARS-CoV-2 infection or vaccination elicit moderate neutralization of SARS-CoV
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