On Sept. 12, 2023, the Centers for Disease Control and Prevention recommended the newly formulated COVID-19 vaccines for all Americans ages 6 months and up, hours after its expert advisory committee voted 13 to 1 in favor of recommending the vaccines.

The CDC’s broad recommendation comes one day after the Food and Drug Administration approved Moderna’s and Pfizer’s updated mRNA vaccines that target a previously dominant variant of the omicron family called XBB.1.5. The updated shots will be available to the public within days.

The Conversation asked Prakash Nagarkatti and Mitzi Nagarkatti, a husband and wife team of immunologists from the University of South Carolina, to weigh in on how the new vaccines might stand up against the latest COVID-19 variants that are swirling across the globe.

1. How are the new vaccines different from the previous?

When the first vaccine against COVID-19 was rolled out in December 2020, it was designed as a monovalent vaccine, meaning that it was formulated against only the original SARS-CoV-2 virus. That vaccine, as well as the updated ones, target the spike protein, which the virus uses to infect our cells and cause the disease.

That design made sense before the virus began mutating into a complex family tree of variants and sublineages. But as the virus structure shifted over time, the antibodies produced in response to the original vaccine became less effective against the new variants.

This necessitated the development in 2022 of new “bivalent” vaccines that targeted both the original strain of SARS‑CoV‑2 and new viral variants such as the omicron BA.4 and BA.5 lineages that were dominant in mid-2022.

But, not surprisingly, new variants of the virus continued to emerge.

In June 2023, the FDA asked vaccine developers to formulate new fall shots to target the then-dominant XBB.1.5 subvariant.

The FDA approved that monovalent mRNA-based vaccine based on the overall efficacy data presented by the vaccine manufacturers.

Unfortunately, XBB.1.5 is no longer the dominant strain in the U.S.; it has been displaced by other variants from the XBB lineage, thereby raising concerns about the potential efficacy of the new shot. As of mid-September, the dominant variants nationwide are EG.5, also known as Eris, followed by FL.1.5.1 – called Fornax – and XBB.1.16.6.

Meanwhile, a new highly mutated omicron offshoot, BA.2.86, nicknamed Pirola, is making its way across the globe – albeit so far in small numbers.

2. Who should get a new shot?

The CDC recommended that everyone ages 6 months old and up should get an updated COVID-19 vaccine so that they can be better protected against developing serious outcomes from COVID-19, including hospitalization. The agency noted that people who received the 2022-2023 bivalent COVID-19 shot “saw greater protection against illness and hospitalization than those who did not.”

Most Americans will be able to get the newly formulated vaccine at no cost, according to the CDC.

The FDA approved a single shot of the updated vaccine for anyone ages 5 and older – regardless of whether they were previously vaccinated or not. The agency also approved unvaccinated individuals 6 months to 4 years of age to receive three doses of the updated Pfizer vaccine or two doses of the updated Moderna vaccine.

3. How effective could the updated shot be against the latest variants?

Based on its current assessment, the CDC indicates that the BA.2.86 variant may be able to cause infection even in people who have been previously vaccinated or those who have had COVID-19 infection in the past. But the CDC says it still expects the updated fall 2023 booster shot to be effective at reducing severe disease and hospitalization.

Moderna reported in August 2023 that the new monovalent mRNA COVID-19 vaccine gave a “significant boost” in antibodies that are protective against two of the currently circulating variants: EG.5 – which is responsible for most cases in the U.S. as of mid-September – and FL.1.5.1. Then, in early September, Moderna announced that its most recent data from human trials showed an 8.7-fold increase in neutralizing antibodies against the newest variant, BA.2.86, following vaccination with the updated shot.

Similarly, new pre-clinical data from Pfizer shows that its version of the new mRNA vaccine produced antibodies that were effective at neutralizing the XBB.1.5, BA.2.86 and EG.5.1 variants.

This early research suggests that the new mRNA vaccines – although developed specifically against XBB.1.5 – are still effective against some of the most prevalent variants.

Novavax, which specializes in traditional protein-based vaccines, also announced in August that its updated COVID-19 vaccine directed against the XBB variant produced a broad neutralizing antibody response against key variants in animal studies. However, the company does not yet have data on its vaccine’s performance against two other key variants, FL.1.5.1 and BA.2.86. The Novavax vaccine has not yet gone up for FDA review, but its approval is also expected within months.

It is important to keep in mind that while all three vaccines have been shown to trigger antibodies that can neutralize most of the currently circulating variants, it is unclear whether the vaccines will be able to effectively prevent COVID-19 infection in humans. Such clinical studies are time-consuming, so given the urgency and speed needed to develop vaccines against the ever-changing COVID-19 variants, vaccine manufacturers rely on antibody levels as an indicator of protection.

4. Is there a ‘right’ time to get the new vaccine?

Antibodies produced after a COVID-19 infection or vaccination last for about six months, and then their levels start declining. This is called “waning immunity.”

About a year after getting a COVID-19 infection or vaccination, only a small fraction of antibodies can be detected. This is why health care providers recommend getting another shot if a year has passed since you were vaccinated or had an active infection.

It has become very clear that vaccines against COVID-19 do not provide 100% protection against catching a new COVID-19 infection, but they can make illness from the infection milder, shorter or both.

In addition, vaccines provide significant protection from hospitalization and death and may help protect against developing long COVID.

Viral infections normally peak in the winter, which is why experts advise getting both COVID-19 and flu vaccine shots in the months of September and October. For convenience, the two shots can be safely taken at the same time. This is because the immune cells that produce antibodies against one vaccine agent are distinct from those that produce antibodies against the other vaccine agent.

However, taking two different vaccines at the same time could cause more side effects, such as fever, aches and pain. This is especially the case for people who have experienced such side effects in the past after taking the COVID-19 and flu vaccines separately.

In addition, a newly approved vaccine against the respiratory syncytial virus, or RSV, is now recommended for people ages 60 and up.

5. Should some people wait for the updated Novavax vaccine?

The Moderna and Pfizer vaccines use the more recent vaccine technology based on mRNA, which instructs the body to produce a protein from a small portion of the SARS-CoV-2 virus. The immune system responds by producing antibodies.

In contrast, the Novavax vaccine relies on a more traditional approach to vaccine production, injecting the viral protein directly into the body to stimulate antibody production. So while the two vaccine types use different pathways to trigger antibodies against the virus, the end result is the same.

The CDC has reported rare cases of myocarditis, which is inflammation of the heart muscle, following vaccination with the Moderna and Pfizer mRNA vaccines. However, the same is true of the Novavax vaccine. So all three vaccines carry this very rare risk.

It is noteworthy that myocarditis is most frequently seen in adolescent and young adult males.

Although some people may have a preference for the traditional protein-based vaccine by Novavax, those who are at higher risk of catching COVID-19 should not wait for the approval of the Novavax vaccine to get their shot.

Prakash Nagarkatti, Professor of Pathology, Microbiology and Immunology, University of South Carolina and Mitzi Nagarkatti, Professor of Pathology, Microbiology and Immunology, University of South Carolina

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Almost like aftershocks, questions about earthquake prediction tend to follow disasters like the one that occurred Sept. 8, 2023, in Morocco. Could advance notice have prevented some of the devastation? Unfortunately, useful predictions are still in the realm of science fiction.

University of Washington professor of seismology and geohazards Harold Tobin heads the Pacific Northwest Seismic Network. He explains the differences between predicting and forecasting earthquakes, as well as early warning systems that are currently in place in some areas.

Can scientists predict a particular earthquake?

In short, no. Science has not yet found a way to make actionable earthquake predictions. A useful prediction would specify a time, a place and a magnitude – and all of these would need to be fairly specific, with enough advance notice to be worthwhile.

For example, if I predict that California will have an earthquake in 2023, that would certainly come true, but it’s not useful because California has many small earthquakes every day. Or imagine I predict a magnitude 8 or greater earthquake will strike in the Pacific Northwest. That is almost certainly true but doesn’t specify when, so it’s not helpful new information.

Earthquakes happen because the slow and steady motions of tectonic plates cause stresses to build up along faults in the Earth’s crust. Faults are not really lines, but planes extending down miles into the ground. Friction due to the enormous pressure from the weight of all the overlying rock holds these cracks together.

An earthquake starts in some small spot on the fault where the stress overcomes the friction. The two sides slip past each other, with the rupture spreading out at a mile or two per second. The grinding of the two sides against each other on the fault plane sends out waves of motion of the rock in every direction. Like the ripples in a pond after you drop in a stone, it’s those waves that make the ground shake and cause damage.

Most earthquakes strike without warning because the faults are stuck – locked up and stationary despite the strain of the moving plates around them, and therefore silent until that rupture begins. Seismologists have not yet found any reliable signal to measure before that initial break.

What about the likelihood of a quake in one area?

On the other hand, earthquake science today has come a long way in what I’ll call forecasting as opposed to prediction.

Seismologists can measure the movement of the plates with millimeter-scale precision using GPS technology and other means, and detect the places where stress is building up. Scientists know about the recorded history of past earthquakes and can even infer farther back in time using the methods of paleoseismology: the geologically preserved evidence of past quakes.

Putting all this information together allows us to recognize areas where conditions are ripe for a fault to break. These forecasts are expressed as the likelihood of an earthquake of a given size or greater in a region over a period of decades into the future. For example, the U.S. Geological Survey estimates the odds of a magnitude 6.7 or greater quake in the San Francisco Bay Area over the next 30 years is 72%.

Are there any hints a quake could be coming?

Only about 1 in 20 damaging earthquakes have foreshocks – smaller quakes that precede a larger one in the same place. By definition they aren’t foreshocks, though, until a bigger one follows. The inability to recognize whether an earthquake in isolation is a foreshock is a big part of why useful prediction still eludes us.

However, in the past decade or so, there have been a number of massive earthquakes of magnitude 8 or more, including the 2011 magnitude 9.0 Tohoku earthquake and tsunami in Japan and a 2014 magnitude 8.1 in Chile. Interestingly, a larger fraction of those very biggest earthquakes seem to have exhibited some precursory events, either in the form of a series of foreshocks detected by seismometers or sped-up movements of the nearby Earth’s crust detected by GPS stations, called “slow slip events” by earthquake scientists.

These observations suggest perhaps there really are precursory signals for at least some huge quakes. Maybe the sheer size of the ensuing quake made otherwise imperceptible changes in the region of the fault prior to the main event more detectable. We don’t know, because so few of these greater than magnitude 8 earthquakes happen. Scientists don’t have a lot of examples to go on that would let us test hypotheses with statistical methods.

In fact, while earthquake scientists all agree that we can’t predict quakes today, there are now essentially two camps: In one view, earthquakes are the result of complex cascades of tiny effects – a sensitive chain reaction of sorts that starts with the proverbial butterfly wing flapping deep within a fault – so they’re inherently unpredictable and will always remain so. On the other hand, some geophysicists believe we may one day unlock the key to prediction, if we can just find the right signals to measure and gain enough experience.

How do early warning systems work?

One real breakthrough today is that scientists have developed earthquake early warning systems like the USGS ShakeAlert now operating in California, Oregon and Washington state. These systems can send out an alert to residents’ mobile devices and to operators of critical machinery, including utilities, hospitals, trains and so on, providing warning of anywhere from a few seconds to more than a minute before shaking begins.

This sounds like earthquake prediction, but it is not. Earthquake early warning relies on networks of seismometers that detect the very beginning of an earthquake on a fault and automatically calculate its location and magnitude before the damaging waves have spread very far. The sensing, calculating and data transfer all happen near the speed of light, while the seismic waves move more slowly. That time difference is what allows early warning.

For example, if an earthquake begins off the coast of Washington state beneath the ocean, coastal stations can detect it, and cities like Portland and Seattle could get tens of seconds of warning time. People may well get enough time to take a life safety action like “Drop, Cover and Hold On” – as long as they are sufficiently far away from the fault itself.

What complications would predicting bring?

While earthquake prediction has often been referred to as the “holy grail” of seismology, it actually would present some real dilemmas if ever developed.

First of all, earthquakes are so infrequent that any early methods will inevitably be of uncertain accuracy. In the face of that uncertainty, who will make the call to take a major action, such as evacuating an entire city or region? How long should people stay away if a quake doesn’t materialize? How many times before it’s a boy-who-cried-wolf situation and the public stops heeding the orders? How do officials balance the known risks from the chaos of mass evacuation against the risk from the shaking itself? The idea that prediction technology will emerge fully formed and reliable is a mirage.

It is often said in the field of seismology that earthquakes don’t kill people, buildings do. Scientists are already good enough today at forecasting earthquake hazards that the best course of action is to redouble efforts to construct or retrofit buildings, bridges and other infrastructure so they’re safe and resilient in the event of ground shaking in any area known to be at risk from large future quakes. These precautions will pay off in lives and property saved far more than a hoped-for means of earthquake prediction, at least for the foreseeable future.

This is an updated version of an article originally published on Feb. 15, 2023.

Harold Tobin, Professor of Seismology and Geohazards, University of Washington

This article is republished from The Conversation under a Creative Commons license. Read the original article.