Being up to date on COVID-19 vaccines means that at this point there have been three or four doses of a single shot. The current boosters are formulations similar to the previously authorized shots, which are based on the original strain of coronavirus that emerged in late 2019. They still protect against severe COVID-19, hospitalizations, and deaths. But as immunity wanes over time and new, more infectious SARS-CoV-2 variants emerge, the world needs a long-term boosting strategy.
I am an immunologist who studies immunity to viruses. I was part of the teams helping Moderna and Johnson & Johnson develop SARS-CoV-2 vaccines, and monoclonal antibody therapies from Eli Lilly and AstraZeneca.
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I am often asked how often, or repeatedly, I think people may need COVID-19 booster shots in the future. No one has the crystal ball to see which SARS-CoV-2 variant will come next or how well the vaccine will ward off immunity in the future. But looking at the other respiratory viral foes that have been plaguing humanity for some time may suggest what the future might look like.
Influenza virus provides an example. It is endemic in humans, meaning it has not disappeared and continues to cause recurrent seasonal waves of infection in populations. Every year officials try to predict the best formulation of the flu shot to reduce the risk of serious illness.
As SARS-CoV-2 continues to evolve and is likely to be endemic, it is possible that people may need booster shots from time to time for the foreseeable future. I suspect scientists will eventually need to update the COVID-19 vaccine to take on new forms, as they do for the flu.
Flu forecasting based on careful monitoring
Influenza virus surveillance provides a possible model for how SARS-CoV-2 may be tracked over time. Flu viruses have caused several pandemics, including the 1918 pandemic that killed an estimated 50 million people worldwide. There are seasonal outbreaks of flu every year, and every year officials encourage the public to get their flu shots.
Each year, health agencies, including the World Health Organization’s Global Influenza Surveillance and Response System, make an educated guess based on flu strains circulating in the Southern Hemisphere about which ones are most likely to spread during the Northern Hemisphere’s upcoming flu season. Is. Then mass production of vaccines based on selected flu strains begins.
In some flu seasons, the vaccine is not a great match with the strains of the virus that end up being the most widely circulated. In those years, the shot isn’t as good at preventing serious disease. While this prediction process is far from perfect, the flu vaccine sector has benefited from robust viral surveillance systems and a concerted international effort to prepare by public health agencies.
While the details of influenza and SARS-CoV-2 viruses differ, I think the COVID-19 sector should consider adopting a similar surveillance system in the long term. Staying on top of the strains that are circulating will help researchers update the SARS-CoV-2 vaccine to match up-to-date variants of the coronavirus.
How SARS-CoV-2 has evolved so far
SARS-CoV-2 faces an evolutionary crisis as it reproduces and spreads from person to person. The virus needs to maintain its ability to enter human cells using its spike proteins, while still changing the ways that allow it to evade vaccine immunity. Vaccines are designed to make your body recognize a particular spike protein, so the more it changes, the more likely the vaccine will be ineffective against the new variant.
Despite these challenges, SARS-CoV-2 and its variants have successfully evolved to become more transmissible and better evade people’s immune responses. During the COVID-19 pandemic, a new SARS-CoV-2 variant of concern has emerged and is dominated by transmission in a series of waves of contagion every four to seven months. Almost like clockwork, the D614G variant emerged in the spring of 2020 and overtook the original SARS-CoV-2 outbreak strain. In late 2020 and early 2021, the Alpha version emerged and dominated the transmission. In mid-2021, the Delta version overtook the Alpha and dominated transmission until it was replaced by the Omicron version in late 2021.
There is no reason to think that this trend will not continue. In the coming months, the world may see a dominant descendant of the various Omicron subvariants. And it’s certainly possible that a newer version will emerge from a non-dominant pool of SARS-CoV-2, which is how Omicron himself came to be.
Current booster shots are additional doses of vaccines based on outbreaks of the long-extinct SARS-CoV-2 virus. The coronavirus variant has changed a lot from the original virus, which does not bode well for continued vaccine efficacy. The idea of tailor-made annual shots — like the flu vaccine — sounds appealing. The problem is that scientists are yet to predict what the next SARS-CoV-2 variant will be with any degree of confidence.
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plans for the future
Yes, the dominant SARS-CoV-2 variant in the upcoming fall and winter season may look different from the currently ongoing Omicron subvariant. But an updated booster that more closely resembles today’s Omicron subvariants, coupled with the immunity people already have from earlier vaccines, will likely provide better protection going forward. This may need to be promoted less frequently – at least as long as the omicron sublineage dominates.
The Food and Drug Administration is set to decide in the coming weeks what degradation boosters should be in time for manufacturers to produce the shots. Vaccine manufacturers such as Moderna are currently testing their booster candidates in people and evaluating immune responses against newly emerging variants. Test results will likely decide what will be used in anticipation of fall or winter growth.
Another possibility is to incorporate a vaccine booster strategy to incorporate universal coronavirus vaccine approaches that are already showing promising in animal studies. Researchers are working on what is called a universal vaccine that would be effective against multiple strains. Some focus on chimeric spikes, which fuse together parts of the spikes of different coronaviruses in a vaccine to broaden protective immunity. Others are experimenting with nanoparticle vaccines that get the immune system to focus on the most vulnerable areas within the coronavirus spike.
These strategies have been shown to prevent difficult-to-prevent SARS-CoV-2 variants in laboratory experiments. They also work against the original SARS virus in animals that caused outbreaks in the early 2000s, as well as zoonotic coronaviruses from bats that may have jumped to humans, leading to future SARS-CoV-3 outbreaks.
Science has provided several safe and effective vaccines that reduce the risk of severe COVID-19. Improving booster strategies, either toward universal-based vaccines or updated boosters, can help us get out of the COVID-19 pandemic.
