Coronavirus news & views

Why Don’t The COVID Vaccines Last Longer?

The FDA just authorized a second booster shot of the Pfizer-BioNTech and Moderna coronavirus vaccines for people over 50 and the CDC has approved it. A second booster has already been approved in the U.K., Sweden, Israel and Denmark.

Why do we need a second booster only months after the first booster, which came only months after most of us received two jabs of either the Pfizer-BioNTech or Moderna mRNA vaccines? Are the vaccines not very good? After all, we get small pox or measles shots that last a lifetime. Others, like the vax for tetanus, last for ~10 years. Why can’t we get a more durable coronavirus vaccine?

The answer is complicated and largely rooted in both viral biology and vaccine immunology.

Viral biology. The simplest answer is that viral mutation can change the molecules the vaccine immune response is trained to recognize, causing vax immunity to decay as viruses mutate. The coronavirus vaccines are directed against the spike protein expressed on the original CoV-2 that first appeared in Wuhan, but that ancestral bug has spawned mutated progeny that look a bit different to the immune system. In other words, viral variants created by “antigenic drift” become less recognizable to the immune system. That is why the vaccines are somewhat less effective against the Omicron variant that carries numerous point mutations in its spike protein. The current vaccines are still pretty effective against current viral variants, but continued antigenic drift along with the selection of variants that can better avoid vaccine immunity will likely require new vaccines in the future.

So, why do we need new flu vaccines every year, and need frequent CoV-2 vaccines, but we don’t similarly need new measles vaccines? Measles, mumps, flu, COVID, and other diseases are caused by viruses, but the different viruses behave quite differently. Viruses carry relatively little genetic material that tends to mutate as they replicate and spread. Some viruses, like flu, also have a “segmented genome” meaning that their genetic material is carried on several separate genetic molecules, making it easy to shuffle their genomes like a deck of cards when different flu strains infect the same animal. Other pathogens carry all their genetic material on a single DNA or RNA molecule making such gene shuffling between strains less likely, but it still happens. Also, the mutation rate of a pathogen’s genome is a function of its replication rate; hence, each time a bug copies its genome, small random errors are inserted into its genetic code. The more the bug replicates, the more mutations will accumulate in its genome and the faster replicating bugs will more rapidly create new variants. Thus, the measles virus is pretty stable since it does not replicate as much as a coronavirus or a flu virus, so it is not surprising that vaccine immunity to measles is much more durable. Smallpox and polioviruses also have relatively low replication rates and vaccine immunity to them also is long-lasting. In contrast, flu and coronaviruses replicate rapidly and pass back and forth between humans and animals. This means that they mutate rapidly and need frequent vaccine updates.

Other vaccines, such as the TB vax, target bacteria not viruses. Bacteria carry larger genomes that are not so changeable, so anti-bacteria vaccines also are pretty long-lasting compared to many anti-viral vaccines.

Yet other vaccines, such as those against tetanus, diphtheria, and pertussis do not even target the pathogen at all, but target toxins produced by the bugs. Vaccinated people produce antibodies that neutralize the toxins and this prevents disease. These vaccines do not forestall infection, they simply prevent the ill effects of the pathogen. Therefore, for these toxoid vaccines, there is no immunological selective pressure to select pathogen variants that can avoid vax immunity. Vaccines against these toxins also tend to be among the longest-lived vaccines.

Vaccine immunology. Vaccines aim to mimic natural immunity we develop to infection with pathogens. By exposing the body to harmless imitations of a pathogen, vaccines create an immune response and immune memory against pathogens, while avoiding the disease caused by the bugs. When an infection does occur in a vaccinated person, a rapid and robust immune response is mounted, first with B-cell generated antibodies that latch onto the invaders and prevent them from spreading and causing illness. Then T-cells secret cytokines that further ramp up the inflammatory response, and other T cells attack pathogen-infected cells. As explained earlier in these pages, antibody responses tend to linger only a few weeks to a few months and then gradually decay. This is good; otherwise your blood serum would be like syrup from all the antibodies against all foreign things you encountered over your lifetime. While antibodies circulating in your blood are good for quickly attacking infections shortly after infection, they do not confer long-term immunity. What confers long-term protection is what are called memory cells. These are a relatively few T and B cells that go dormant after fighting an initial infection or responding to a vaccine, but hang around awaiting a new infection to signal them to quickly roar back to life and mount a vigorous response against their cognate pathogen. This secondary response to a previously seen pathogen is much faster and usually nips the bug in the bud so you don’t even know you were infected.

When we hear that CoV-2 immunity decays only a few months after vaccination, the reports usually refer to declining levels of anti-CoV-2 antibodies, which happens naturally. Such announcements do not take into account your immune memory, which is harder to measure, but which is a better metric of your long term immunity. The problem also is that we simply have not had enough time with the vaccines to know how long their immune memory persists. It seems relevant that a study published in July 2020 reported that people who were infected with SARS in 2003 maintained robust T cell immunity 17 years later. So far, indications are that even though antibody levels fall over time, immunological memory after vaccination also remains robust. This is seen by the continued protection from serious disease and death in vaccinated people with low antibody levels. The vaccines and the immune memory they stimulate are working. How long that memory persists is unknown. Time will tell.

So why are we getting the booster shots? In the face of a raging pandemic caused by a novel pathogen, the cautious approach is to keep antibody levels at a protective level in vaccinated people until we better understand the extent of long-term protection brought on by our immune memory. The boosters, therefore, represent a cautious approach to maintain an effective antibody defense during these still early months of a novel pandemic. We likely will reach a time where world-wide immunity from vaccination and natural infection will give us baseline protection that will render COVID-19 mostly a bothersome disease rather than a life threatening infection. Until then, the boosters are a good idea to help us maintain an effective antibody defense against serious disease.

The natural pathology of measles is instructive here. Even though antibody levels typically decline after most immunizations, antibodies produced after a measles vaccine persist for many years. This happens with some other, but not all, vaccines too, but why? In countries where the measles virus is endemic, repeated infection of vaccinated people keeps the antibody immune response in continual high gear. That is not the case with the flu virus which changes rapidly and bypasses last years shot. Interestingly, measles has been eradicated from the US and Western Europe, so vaccinated people are not continually exposed and re-exposed to the virus and, unlike for those who live in endemic areas, our anti-measles antibody levels decline. Therefore, our long-term protection against the virus is due to our immune memory and not due to antibody levels.

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The History Of Vaccine Mandates In The US

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As employers and the President are pushing vaccine mandates because too many have refused them, voices are crying out for their perceived rights saying “my body my choice.” They do not like their bosses or the government telling them to get vaccinated. This is a clash between individual rights and public health measures designed to save lives and to protect the larger community. Who gets to make the key decisions? How far can the government and employers go? Do individual rights trump community safety?

On Sept. 9, Biden announced the most sweeping vaccine requirements in American history, ordering that businesses with 100 or more employees ensure that all their workers are either vaccinated or get tested weekly for the coronavirus. The new rules also require vaccinations for federal workers and for federal contractors, as well as for workers at healthcare facilities that receive funding from Medicare and Medicaid. This will affect about 100 million people.

The authority for these government mandates, claims Biden, is a 1970 federal statute that gives the Secretary of Labor authority to issue a six month Emergency Temporary Standard (ETS) to protect workers from “grave danger from exposure to substances or agents determined to be toxic or physically harmful.” His move has triggered a political and legal battle, with many Republican governors vowing to fight the mandates in court. The mandates raise several new questions regarding this vague statute: Is a virus a “…toxic or physically harmful substance?” Does COVID-19 present a “grave danger?” Has the executive branch exceeded its authority in offering a solution to a problem previously reserved to the states? Do these mandates violate the 14th Amendment by depriving workers of their personal liberties? It is important to note that Biden’s mandates do not actually make vaccines compulsory: The government may levy a fine or forbid a child from attending school, but no American will be forced to get an unwanted jab. This has not always been the case.

There are historical precedents for vaccine mandates and even for forced vaccination.

In February 1991, five Philadelphia children died from measles, a disease that was mostly eradicated in the US, due to vaccination. Measles once sickened millions of kids, each year hospitalizing ~50,000 and killing close to 500 before a successful vaccine was developed in 1963. After that, cases dropped dramatically as all states mandated measles shots for school children. Vaccine hesitancy and resistance were rare because people saw the tangible success of the measles vaccine.

But, in Philadelphia that winter of 1991, the serious cases of measles came from a single source, a church cult that rejected “…all means of healing apart from God’s way.” Church members took no medicines, owned no thermometers, and saw no doctors. Rejecting all birth control, they raised large families in close quarters, a recipe for the measles epidemic, which they cooked. Trying to contain the threat to the rest of the city, officials worked through the courts to gain access to the homes of the congregants and received the authority to vaccinate the children against the wishes of their parents. In this public health emergency, defending the parents’ anti-vax actions was close to impossible. Even the ACLU took a pass.

Vaccine mandates even appeared during the Revolutionary War. George Washington mandated that all his troops be immunized against smallpox, even against their will. He described smallpox to Virginia’s Governor Patrick Henry as “more destructive to an Army in a Natural Way, than the Enemy’s Sword.” As I wrote earlier in these pages, smallpox had doomed the Colonial Army’s assault on Quebec in 1775, and it threatened Washington’s main force. Washington’s mandate proved a brilliant gambit and smallpox largely disappeared from the ranks. Some historians point to the mandate as a major factor in winning the war against the Brits.

During that war, smallpox vaccination entailed a primitive vaccination procedure known as variolation. That involved opening a lesion from an infected person and scraping its contents into the arm of a recipient. It was effective, but the vaccinated person became quite ill for a couple of weeks, and about 3% of them died from the pox. Later, in 1796, the English scientist Edward Jenner discovered a much safer method of immunization using cowpox, a virus similar to smallpox that did not cause significant disease in people. But the new smallpox vaccine got a mixed reception in the US as some resisted it for reasons of personal safety based on the variolation experience. They rationalized, “what good could possibly come from polluting the body with dangerous foreign matter?” Or, “Why challenge the plans of the Creator?” Still, Jenner’s vaccine was a clear improvement over variolation and drove a steady decline in smallpox outbreaks throughout the 19th century. States began passing laws mandating smallpox vaccinations for school children, and some forcibly vaccinated prisoners, paupers, and orphans.

In 1905, the issue of vaccine mandates reached the Supreme Court in the seminal case of Jacobson v. Massachusetts. Henning Jacobson, a Lutheran pastor in Cambridge had defied a city ordinance requiring smallpox vaccinations during an outbreak. He refused to pay a $5 fine so he was arrested. Jacobson posited that “healthy and law-abiding” people like himself (even though he was disobeying the law at the time) posed a minimal danger to the community. He argued that even if his refusal to be vaccinated led to him spreading the smallpox virus, the only victims would be others “who failed or refused to be vaccinated.” In other words, he reasoned that it would be ok to not get the vax because the vaxed would be safe, but wholly ignored the rights to safety of those who were not vaxed. 

It is an argument that is repeated today about the CoV-2 vax. Using modern science that was not available in the early 20^th century, experts have repeatedly refuted this argument, explaining that many people who want the vax cannot be fully vaccinated because they are immunocompromised, or allergic to the vaccine’s contents, or do not have access to the vaccine. Also, we now know that the more RNA viruses, like the coronavirus, are allowed to spread, the greater the chance more deadly variants can appear. Jacobson’s contention that the decision to vaccinate solely belongs to the individual, not to the state, employers, or to medical authorities remains a central tenant of today's anti-vaxers.

The Supreme Court disagreed with Jacobson. The majority opinion, written by Justice John Marshall Harlan, asserted that “the liberty secured by the Constitution does not import an absolute right in each person to be at all times, and in all circumstances, wholly freed from restraint.” Rather, he argued, the Constitution rests upon “the fundamental principle of the social compact…that all shall be governed by certain laws for the protection, safety, prosperity and happiness of the people, and not for the profit, honor or private interests of any one man, family or class of men.” Jacobson had not only broken the law, the court suggested he also had violated the principle upon which a well-ordered society depends. We are not wholly independent the court ruled. The greater good of the community can trump individual rights.

Using Jacobson as precedent, the Supreme Court in 1922, upheld a local ordinance in San Antonio requiring proof of smallpox vaccination for people entering “public schools or other places of education.”  

Later, during World War II, the US military made vaccines mandatory for a host of diseases, such as typhoid, yellow fever and tetanus, and it still mandates certain vaccines for troops in certain deployments. Soon after the war very successful vaccines were developed against several childhood diseases like polio, measles, mumps and chickenpox. Guided by the Supreme Court’s ruling in Jacobson, all 50 states put laws on the books mandating many of these vaccinations for school children. Even today, many school districts and colleges mandate certain vaccines for students and staff. Hospitals, too, often mandate certain vaccines for their staff. Until lately, vaccine mandates have not generated much angst and anger.

Why is this? Perhaps vaccines have done their job too well: Many of them have erased the tragic evidence of why they were needed in the first place. The world no longer deals with small pox, thanks to the vaccine. Almost no one in this country has seen someone ravaged by polio, or a child hospitalized with measles, or who lost his hearing due to chicken pox, all thanks to vaccines. Yet, now with COVID-19, anti-vaccine anxieties have found their way into the political mainstream, especially among conservatives. An estimated 80 million American adults remain unvaccinated against COVID and represent potential factories for producing the next deadly coronavirus variant, which is very preventable.

As I have addressed before in these pages, many factors fuel resistance to the life-saving shots, including doubts about their quick development and their possible long-term effects. But a growing distrust of professional expertise, including medical science, has also played a role, which is unwarranted. Who are you going to believe, a medical scientist like me with nothing to gain in the debate (except the safety of my friends, family, and self), or someone who read a web post from folks who are selling nostrums they claim will protect you, like Dr. Steve Hotze, or from one of America’s Frontline Doctors whose web site claimed that gynecological problems were caused by having sex with demons? Do you jump on the side of those who tout that their individual freedoms have been abridged, but who do not consider the freedoms from disease of the greater community, and whom the courts already have decided against?

Almost 300 years ago, Benjamin Franklin struggled over whether to have his sons variolated against smallpox. In his “Autobiography,” he worried that well-meaning people were tragically misjudging the calculus between the risks and benefits of the procedure, as he had once done, with a tragic result. He wrote, “In 1736, I lost one of my sons, a fine boy of four years old, by the smallpox….I long regretted bitterly and still regret that I had not given it to him by inoculation. This I mention for the sake of the parents who omit that operation, on the supposition that they should never forgive themselves if a child died under it; my example showing that the regret may be the same either way, and that, therefore, the safer should be chosen.”