Pharmaceutical company executives have been hinting for months that booster shots will be necessary to maintain the efficacy of COVID-19 vaccines. A study of such boosters is already underway. But the companies that stand to profit from these shots shouldn’t get to unilaterally determine the need for a repeat mass vaccination campaign without scientific questioning. Moreover, focus groups among the vaccine-hesitant have shown that talk of boosters can decrease the likelihood of people getting a vaccine now.
Bodies of scientific research indicate that your immune system should offer you long-lived protection from reinfection if you’ve been vaccinated, even with the emergence of more infectious variants.
I’m going to take you through that science so you don’t have to worry. And so that you can help doctors like me advocate for industry and public officials to devote their efforts to more important pursuits, like making sure other countries have enough vaccines to end this pandemic.
In brief, there are two major arms of the immune system: B cells (which produce disease-fighting antibodies) and T cells, which attack specific parts (called “epitopes”) of a dangerous pathogen. T cells are divided into two types, specially CD4 cells (“helper” T cells) and CD8 cells (“cytotoxic” T cells). Each of these arms, once stimulated by infection or vaccine, makes “memory” banks which — when working properly — come roaring back to attack the virus and protect you from getting sick.
With that in mind, here are seven reasons why you shouldn’t have to worry about getting a booster.
COVID vaccines are highly effective and work against variants
COVID-19 vaccines work very well in the real world. And T cell responses from vaccination are robust against even the most potent variants. Antibody responses from vaccination may be slightly lower against certain COVID-19 variants, but T cell immunity has been shown to be unperturbed by the variants’ notorious mutations in the spike protein. T cell responses after mRNA vaccines (Moderna or Pfizer) maintained their strength against different variants, including P.1 Brazil variant, B.1.1.7 UK variant, B.1.351 South Africa variant and the CA.20.C California variant. A few mutations to the spike protein (even as many as 13) cannot knock out such a robust T cell response.
Vaccines help you form antibody-producing memory B cells
In one study, 12 volunteers who had never had COVID-19, and were fully vaccinated with two mRNA vaccine shots, underwent biopsies of their lymph nodes — where antibody-producing memory B cells are stored in places called “germinal centers.” These biopsies showed that memory B cells were formed in response to the vaccine. And they increased in concentration three, four, six and seven weeks after the first shot.
Natural infection also generates memory B cells.
Of course, antibody levels wane over time. That’s a normal adaption of the immune system, otherwise, antibodies from multiple infections seen in the past would clog up our blood. But with COVID-19, strong memory B cells were detected in individuals six and eight-months after infection.
Once memory B cells are formed, they last a long time
Memory B cells are extraordinary things. They can produce neutralizing antibodies even when facing an infection decades later. One amazing study (published in 2008) looked at 32 individuals aged 91-101 years who survived the 1918 influenza pandemic. Memory B cells against the 1918 strain were isolated from the subjects’ blood and then exposed to the 1918 virus in a test tube. They still generated high levels of neutralizing antibodies, which were strong enough to protect mice from lethal infection.
Immunity isn’t just about antibodies
Antibodies are only a small portion of assessing vaccination efficacy. But there continues to be an outsized emphasis on them because they were formerly the only facet of vaccine response science knew how to calculate. Pathogen-specific T cell response measurements, like we have now for COVID-19, take sophisticated technology. But they’re important. T cell responses in vaccinations for other pathogens have been shown to be long-lasting. In one study of 56 volunteers who were vaccinated for measles as kids, strong T cell responses to vaccination were measured up to 34 years later.
Vaccines and natural infection trigger strong memory T cell immunity
All trials of the major COVID-19 vaccines showed powerful T cell immunity following vaccination. A number of other studies demonstrate production of strong T cell immunity to COVID-19 after natural infection, even mild or asymptomatic infection. The half-lives of memory T cells formed after COVID-19 infection are long. One study found that eight months after the initial infection, memory T cells were comparable to those observed after yellow fever immunization (a vaccine usually given only once over a lifetime).
T cell immunity in other severe coronaviruses is long-lasting
SARS-CoV-2, which causes COVID-19, is an outlier among coronaviruses in that it causes severe disease. Coronaviruses are usually no more dangerous than the common cold for which they are responsible. But there have been two other coronaviruses in the recent past that caused severe disease: Severe Acute Respiratory Distress Syndrome (SARS) in late 2003 and Middle East Respiratory Syndrome (MERS) in 2011. A study performed in 2020 demonstrated that 23 recovered SARS patients possessed long-lasting memory T cells in their blood. And these cells were still reactive to SARS nearly two decades after the outbreak in 2003.
Coronaviruses don’t mutate quickly
Influenza requires annual booster shots because of the speed of its mutations. Coronaviruses are RNA viruses, like influenza and HIV (a retrovirus), but do not mutate as quickly as either. This is because their replicating mechanism (polymerase) has a strong proofreading mechanism. If the virus mutates it usually goes back and self-corrects. Mutations can and do arise when transmission is high, as we have seen in recent months. However, the COVID-19 virus will not mutate like this when we tamp down transmission with mass vaccination.
Immunity from natural infection or vaccination to COVID-19 is likely to be durable, even against variants. With a 77% one-shot vaccination rate, San Francisco is well on its way to ending its epidemic. The best way to keep people safe now is to put the discussion of boosters aside and work hard on global vaccine distribution.
Monica Gandhi is an infectious diseases doctor and Professor of Medicine at University of California San Francisco. She serves as the Director of the UCSF Center for AIDS Research and medical director of the Ward 86 HIV Clinic. @MonicaGandhi9
May 25, 2021 at 06:03PM
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No, you probably won't need a COVID vaccine booster shot, says UCSF's Monica Gandhi - San Francisco Chronicle
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