Be aware of COVID-19 vaccines means: had three or four doses of the same shot at this point. Current boosters are the same formulations as the first authorized shots, based on the original strain of the coronavirus which emerged at the end of 2019. They still protect against severe COVID-19, hospitalizations and deaths.
But as immunity wanes over time and new ones become more contagious SARS-CoV-2 variants arise, the world needs a long-term strategy.
I am an immunologist who studies immunity to? viruses† I was part of the teams that helped develop the Moderna and Johnson & Johnson SARS-CoV-2 Vaccinesand the monoclonal antibody therapies by Eli Lilly and AstraZeneca.
I am often asked how often, or infrequently, I think people are likely to need COVID-19 booster injections in the future. No one has a crystal ball to see which SARS-CoV-2 variant will be next or how good future variants will be at evading vaccine immunity. But looking at other respiratory viral foes that have plagued humanity for some time can give an idea of what the future might look like.
Influenza virus provides an example. It is endemic to humans, meaning it has not disappeared and still causes recurring seasonal waves of infection in the population. Every year, officials try to predict the best formulation of a flu shot to reduce the risk of serious illness.
As SARS-CoV-2 continues to develop and likely to become endemic, it’s possible that people will need periodic booster shots in the near future. I suspect that eventually scientists will have to update the COVID-19 vaccine to adopt newer variants, such as with the flu.
Predicting flu based on careful surveillance
Influenza virus surveillance provides a potential model for how to track SARS-CoV-2 over time. Flu viruses have caused several pandemics, including the one in 1918 that killed people an estimated 50 million people worldwide† Every year there are seasonal outbreaks of flu, and every year officials encourage the public to: get their flu shots†
Every year, health authorities, including the World Health Organisation‘s Global Flu Surveillance and Response System make an educated guess based on the flu strains circulating in the southern hemisphere about which strains are most likely to be circulating in the upcoming flu season in the northern hemisphere. Then the large-scale vaccine production starts, based on the selected flu strains.
Some flu seasons, the vaccine doesn’t seem to work great match with the virus strains which eventually circulate the most. Those years, the shot is not so good at preventing serious diseases. While this forecasting process is far from perfect, the flu vaccine field has benefited from strong viral surveillance systems and a concerted international effort by public health agencies to prepare.
While the specifics for influenza and SARS-CoV-2 viruses are different, I think the COVID-19 field should consider adopting similar long-term surveillance systems. Keeping track of which strains are circulating helps researchers update SARS-CoV-2 vaccine so it’s up to date coronavirus variants.
How SARS-CoV-2 has evolved so far
SARS-CoV-2 faces an evolutionary dilemma as it reproduces and spreads from person to person. The virus must maintain its ability to enter human cells using its spike protein, while still altering it in such a way that it can 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 not be effective against the new variant.
Despite these challenges, SARS-CoV-2 and its variants have successfully evolved to be more transmissible and better evade humans’ immune responses. In the course of the COVID-19 pandemica new SARS-CoV-2 variant of concern has emerged and dominates transmission in a series of waves of infection every four to seven months.
Almost like clockwork, the D614G variant appeared in the spring of 2020 and overtook the original SARS-CoV-2 outbreak strain. In late 2020 and early 2021, the alpha variant appeared and the transmission dominated. In mid-2021, the delta variant overtook alpha and then dominated the transmission until it was supplanted by the Omicron variant in late 2021.
There is no reason to believe that this trend will not continue. In the coming months, the world could become a dominant descendant of the various ommicron subvariants† And it’s certainly possible that a new variant will emerge from a non-dominant pool of SARS-CoV-2, thus creating omicron itself.
The current booster shots are simply extra doses of the vaccines based on the SARS-CoV-2 virus outbreak that has long been extinct. The coronavirus variants have changed a lot from the original virus, which does not bode well for the continued efficacy of the vaccine. The idea of tailor-made annual injections – such as the flu vaccine – sounds appealing. The problem is that scientists have not yet been able to predict with any certainty what the next SARS-CoV-2 variant will be.
Plans for the future
Yes, the dominant SARS-CoV-2 variants in the coming fall and winter seasons may look different from the omicron subvariants currently circulating. But an updated booster that is more similar to current omicron subvariants, combined with the immunity people already have from the first vaccines, is likely to provide better protection in the future. Less frequent boosting may be needed – at least as long as ommicron sublines continue to dominate.
The Food and Drug Administration will meet in the coming weeks to decide what the fall boosters should be so manufacturers can produce the shots. Vaccine makers like Moderna are currently testing their booster candidates in humans and evaluating the immune response against newly emerging variants† The test results will likely decide what will be used in anticipation of a fall or winter wave.
Another possibility is to flip the vaccine-booster strategy to include universal approaches to the coronavirus vaccine that already look promising in animal studies. Researchers are working on a so-called universal vaccine that would be effective against multiple strains.
Some focus on chimeric peaksthat fuse parts of the peak of different coronaviruses into one vaccine, to broaden protective immunity. Others experiment with vaccines against nanoparticles that cause the immune system to target the most vulnerable regions within the coronavirus peak.
These strategies have been shown to ward off hard-to-stop SARS-CoV-2 variants in lab experiments. They also work in animals against the original SARS virus that caused an outbreak in the early 2000s, and against zoonotic bat coronaviruses that could jump into humans and cause a future SARS-CoV-3 outbreak.
Science has provided several safe and effective vaccines that reduce the risk of severe COVID-19. Reformulating booster strategies, either towards universal vaccines or updated boosters, could help us get out of the COVID-19 pandemic.
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