How COVID-19 Immunity Holds Up Over Time
Posted on by Lawrence Tabak, D.D.S., Ph.D.
More than 215 million people in the United States are now fully vaccinated against the SARS-CoV-2 virus responsible for COVID-19 . More than 40 percent—more than 94 million people—also have rolled up their sleeves for an additional, booster dose. Now, an NIH-funded study exploring how mRNA vaccines are performing over time comes as a reminder of just how important it will be to keep those COVID-19 vaccines up to date as coronavirus variants continue to circulate.
The results, published in the journal Science Translational Medicine, show that people who received two doses of either the Pfizer or Moderna COVID-19 mRNA vaccines did generate needed virus-neutralizing antibodies . But levels of those antibodies dropped considerably after six months, suggesting declining immunity over time.
The data also reveal that study participants had much reduced protection against newer SARS-CoV-2 variants, including Delta and Omicron. While antibody protection remained stronger in people who’d also had a breakthrough infection, even that didn’t appear to offer much protection against infection by the Omicron variant.
The new study comes from a team led by Shan-Lu Liu at The Ohio State University, Columbus. They wanted to explore how well vaccine-acquired immune protection holds up over time, especially in light of newly arising SARS-CoV-2 variants.
This is an important issue going forward because mRNA vaccines train the immune system to produce antibodies against the spike proteins that crown the surface of the SARS-CoV-2 coronavirus. These new variants often have mutated, or slightly changed, spike proteins compared to the original one the immune system has been trained to detect, potentially dampening the immune response.
In the study, the team collected serum samples from 48 fully vaccinated health care workers at four key time points: 1) before vaccination, 2) three weeks after the first dose, 3) one month after the second dose, and 4) six months after the second dose.
They then tested the ability of antibodies in those samples to neutralize spike proteins as a correlate for how well a vaccine works to prevent infection. The spike proteins represented five major SARS-CoV-2 variants. The variants included D614G, which arose very soon after the coronavirus first was identified in Wuhan and quickly took over, as well as Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), and Omicron (B.1.1.529).
The researchers explored in the lab how neutralizing antibodies within those serum samples reacted to SARS-CoV-2 pseudoviruses representing each of the five variants. SARS-CoV-2 pseudoviruses are harmless viruses engineered, in this case, to bear coronavirus spike proteins on their surfaces. Because they don’t replicate, they are safe to study without specially designed biosafety facilities.
At any of the four time points, antibodies showed a minimal ability to neutralize the Omicron spike protein, which harbors about 30 mutations. These findings are consistent with an earlier study showing a significant decline in neutralizing antibodies against Omicron in people who’ve received the initial series of two shots, with improved neutralizing ability following an additional booster dose.
The neutralizing ability of antibodies against all other spike variants showed a dramatic decline from 1 to 6 months after the second dose. While there was a marked decline over time after both vaccines, samples from health care workers who’d received the Moderna vaccine showed about twice the neutralizing ability of those who’d received the Pfizer vaccine. The data also suggests greater immune protection in fully vaccinated healthcare workers who’d had a breakthrough infection with SARS-CoV-2.
In addition to recommending full vaccination for all eligible individuals, the Centers for Disease Control and Prevention (CDC) now recommends everyone 12 years and up should get a booster dose of either the Pfizer or Moderna vaccines at least five months after completing the primary series of two shots . Those who’ve received the Johnson & Johnson vaccine should get a booster at least two months after receiving the initial dose.
While plenty of questions about the durability of COVID-19 immunity over time remain, it’s clear that the rapid deployment of multiple vaccines over the course of this pandemic already has saved many lives and kept many more people out of the hospital. As the Omicron threat subsides and we start to look forward to better days ahead, it will remain critical for researchers and policymakers to continually evaluate and revise vaccination strategies and recommendations, to keep our defenses up as this virus continues to evolve.
 COVID-19 vaccinations in the United States. Centers for Disease Control and Prevention. February 27, 2022.
 Neutralizing antibody responses elicited by SARS-CoV-2 mRNA vaccination wane over time and are boosted by breakthrough infection. Evans JP, Zeng C, Carlin C, Lozanski G, Saif LJ, Oltz EM, Gumina RJ, Liu SL. Sci Transl Med. 2022 Feb 15:eabn8057.
 COVID-19 vaccine booster shots. Centers for Disease Control and Prevention. Feb 2, 2022.
COVID-19 Research (NIH)
Shan-Lu Liu (The Ohio State University, Columbus)
NIH Support: National Institute of Allergy and Infectious Diseases; National Cancer Institute; National Heart, Lung, and Blood Institute; Eunice Kennedy Shriver National Institute of Child Health and Human Development
Accelerating COVID-19 Vaccine Testing with ‘Correlates of Protection’
Posted on by Dr. Francis Collins
With Omicron now on so many people’s minds, public health officials and virologists around the world are laser focused on tracking the spread of this concerning SARS-CoV-2 variant and using every possible means to determine the effectiveness of our COVID-19 vaccines against it. Ultimately, the answer will depend on what happens in the real world. But it will also help to have a ready laboratory means for gauging how well a vaccine works, without having to wait many months for the results in the field.
With this latter idea in mind, I’m happy to share results of an NIH-funded effort to understand the immune responses associated with vaccine-acquired protection against SARS-CoV-2 . The findings, based on the analysis of blood samples from more than 1,000 people who received the Moderna mRNA vaccine, show that antibody levels do correlate, albeit somewhat imperfectly, with how well a vaccine works to prevent infection.
Such measures of immunity, known as “correlates of protection,” have potential to support the approval of new or updated vaccines more rapidly. They’re also useful to show how well a vaccine will work in groups that weren’t represented in a vaccine’s initial testing, such as children, pregnant women, and those with certain health conditions.
The latest study, published in the journal Science, comes from a team of researchers led by Peter Gilbert, Fred Hutchinson Cancer Research Center, Seattle; David Montefiori, Duke University, Durham, NC; and Adrian McDermott, NIH’s Vaccine Research Center, National Institute of Allergy and Infectious Diseases.
The team started with existing data from the Coronavirus Efficacy (COVE) trial. This phase 3 study, conducted in 30,000 U.S. adults, found the Moderna vaccine was safe and about 94 percent effective in protecting people from symptomatic infection with SARS-CoV-2 .
The researchers wanted to understand the underlying immune responses that afforded that impressive level of COVID-19 protection. They also sought to develop a means to measure those responses in the lab and quickly show how well a vaccine works.
To learn more, Gilbert’s team conducted tests on blood samples from COVE participants at the time of their second vaccine dose and again four weeks later. Two of the tests measured concentrations of binding antibodies (bAbs) that latch onto spike proteins that adorn the coronavirus surface. Two others measured the concentration of more broadly protective neutralizing antibodies (nAbs), which block SARS-CoV-2 from infecting human cells via ACE2 receptors found on their surfaces.
Each of the four tests showed antibody levels that were consistently higher in vaccine recipients who did not develop COVID-19 than in those who did. That is consistent with expectations. But these data also allowed the researchers to identify the specific antibody levels associated with various levels of protection from disease.
For those with the highest antibody levels, the vaccine offered an estimated 98 percent protection. Those with levels about 1,000 times lower still were well protected, but their vaccine efficacy was reduced to about 78 percent.
Based on any of the antibodies tested, the estimated COVID-19 risk was about 10 times lower for vaccine recipients with antibodies in the top 10 percent of values compared to those with antibodies that weren’t detectable. Overall, the findings suggest that tests for antibody levels can be applied to make predictions about an mRNA vaccine’s efficacy and may be used to guide modifications to the current vaccine regimen.
To understand the significance of this finding, consider that for a two-dose vaccine like Moderna or Pfizer, a trial using such correlates of protection might generate sufficient data in as little as two months . As a result, such a trial might show whether a vaccine was meeting its benchmarks in 3 to 5 months. By comparison, even a rapid clinical trial done the standard way would take at least seven months to complete. Importantly also, trials relying on such correlates of protection require many fewer participants.
Since all four tests performed equally well, the researchers say it’s conceivable that a single antibody assay might be sufficient to predict how effective a vaccine will be in a clinical trial. Of course, such trials would require subsequent real-world studies to verify that the predicted vaccine efficacy matches actual immune protection.
It should be noted that the Food and Drug Administration (FDA) would need to approve the use of such correlates of protection before their adoption in any vaccine trial. But, to date, the totality of evidence on neutralizing antibody responses as correlates of protection—for which this COVE trial data is a major contributor—is impressive.
Neutralizing antibody levels are also now being considered for use in future coronavirus vaccine trials. Indeed, for the EUA of Pfizer’s mRNA vaccine for 5-to-11-year-olds, the FDA accepted pre-specified success criteria based on neutralizing antibody responses in this age group being as good as those observed in 16- to 25-year-olds .
Antibody levels also have been taken into consideration for decisions about booster shots. However, it’s important to note that antibody levels are not precise enough to help in deciding whether or not any particular individual needs a COVID-19 booster. Those recommendations are based on how much time has passed since the original immunization.
Getting a booster is a really good idea heading into the holidays. The Delta variant remains very much the dominant strain in the U.S., and we need to slow its spread. Most experts think the vaccines and boosters will also provide some protection against the Omicron variant—though the evidence we need is still a week or two away. The Centers for Disease Control and Prevention (CDC) recommends a COVID-19 booster for everyone ages 18 and up at least six months after your second dose of mRNA vaccine or two months after receiving the single dose of the Johnson & Johnson vaccine . You may choose to get the same vaccine or a different one. And, there is a place near you that is offering the shot.
 Immune correlates analysis of the mRNA-1273 COVID-19 vaccine efficacy clinical trial.
Gilbert PB, Montefiori DC, McDermott AB, Fong Y, Benkeser D, Deng W, Zhou H, Houchens CR, Martins K, Jayashankar L, Castellino F, Flach B, Lin BC, O’Connell S, McDanal C, Eaton A, Sarzotti-Kelsoe M, Lu Y, Yu C, Borate B, van der Laan LWP, Hejazi NS, Huynh C, Miller J, El Sahly HM, Baden LR, Baron M, De La Cruz L, Gay C, Kalams S, Kelley CF, Andrasik MP, Kublin JG, Corey L, Neuzil KM, Carpp LN, Pajon R, Follmann D, Donis RO, Koup RA; Immune Assays Team§; Moderna, Inc. Team§; Coronavirus Vaccine Prevention Network (CoVPN)/Coronavirus Efficacy (COVE) Team§; United States Government (USG)/CoVPN Biostatistics Team§. Science. 2021 Nov 23:eab3435.
 Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine. Baden LR, El Sahly HM, Essink B, Kotloff K, Frey S, Novak R, Diemert D, Spector SA, Rouphael N, Creech CB, McGettigan J, Khetan S, Segall N, Solis J, Brosz A, Fierro C, Schwartz H, Neuzil K, Corey L, Gilbert P, Janes H, Follmann D, Marovich M, Mascola J, Polakowski L, Ledgerwood J, Graham BS, Bennett H, Pajon R, Knightly C, Leav B, Deng W, Zhou H, Han S, Ivarsson M, Miller J, Zaks T; COVE Study Group. N Engl J Med. 2021 Feb 4;384(5):403-416.
 A government-led effort to identify correlates of protection for COVID-19 vaccines. Koup RA, Donis RO, Gilbert PB, Li AW, Shah NA, Houchens CR. Nat Med. 2021 Sep;27(9):1493-1494.
 Evaluation of the BNT162b2 Covid-19 vaccine in children 5 to 11 years of age. Walter EB, Talaat KR, Sabharwal C, Gurtman A, Lockhart S, Paulsen GC, Barnett ED, Muñoz FM, Maldonado Y, Pahud BA, Domachowske JB, Simões EAF, Sarwar UN, Kitchin N, Cunliffe L, Rojo P, Kuchar E, Rämet M, Munjal I, Perez JL, Frenck RW Jr, Lagkadinou E, Swanson KA, Ma H, Xu X, Koury K, Mather S, Belanger TJ, Cooper D, Türeci Ö, Dormitzer PR, Şahin U, Jansen KU, Gruber WC; C4591007 Clinical Trial Group. N Engl J Med. 2021 Nov 9:NEJMoa2116298.
 COVID-19 vaccine booster shots. Centers for Disease Control and Prevention. Nov 29, 2021.
COVID-19 Research (NIH)
Combat COVID (U.S. Department of Health and Human Services)
Peter Gilbert (Fred Hutchison Cancer Research Center)
David Montefiori (Duke University, Durham, NC)
Adrian McDermott (National Institute of Allergy and Infectious Diseases/NIH)
NIH Support: National Institute of Allergy and Infectious Diseases
mRNA Vaccines May Pack More Persistent Punch Against COVID-19 Than Thought
Posted on by Dr. Francis Collins
Many people, including me, have experienced a sense of gratitude and relief after receiving the new COVID-19 mRNA vaccines. But all of us are also wondering how long the vaccines will remain protective against SARS-CoV-2, the coronavirus responsible for COVID-19.
Earlier this year, clinical trials of the Moderna and Pfizer-BioNTech vaccines indicated that both immunizations appeared to protect for at least six months. Now, a study in the journal Nature provides some hopeful news that these mRNA vaccines may be protective even longer .
In the new study, researchers monitored key immune cells in the lymph nodes of a group of people who received both doses of the Pfizer-BioNTech mRNA vaccine. The work consistently found hallmarks of a strong, persistent immune response against SARS-CoV-2 that could be protective for years to come.
Though more research is needed, the findings add evidence that people who received mRNA COVID-19 vaccines may not need an additional “booster” shot for quite some time, unless SARS-CoV-2 evolves into new forms, or variants, that can evade this vaccine-induced immunity. That’s why it remains so critical that more Americans get vaccinated not only to protect themselves and their loved ones, but to help stop the virus’s spread in their communities and thereby reduce its ability to mutate.
The new study was conducted by an NIH-supported research team led by Jackson Turner, Jane O’Halloran, Rachel Presti, and Ali Ellebedy at Washington University School of Medicine, St. Louis. That work builds upon the group’s previous findings that people who survived COVID-19 had immune cells residing in their bone marrow for at least eight months after the infection that could recognize SARS-CoV-2 . The researchers wanted to see if similar, persistent immunity existed in people who hadn’t come down with COVID-19 but who were immunized with an mRNA vaccine.
To find out, Ellebedy and team recruited 14 healthy adults who were scheduled to receive both doses of the Pfizer-BioNTech vaccine. Three weeks after their first dose of vaccine, the volunteers underwent a lymph node biopsy, primarily from nodes in the armpit. Similar biopsies were repeated at four, five, seven, and 15 weeks after the first vaccine dose.
The lymph nodes are where the human immune system establishes so-called germinal centers, which function as “training camps” that teach immature immune cells to recognize new disease threats and attack them with acquired efficiency. In this case, the “threat” is the spike protein of SARS-COV-2 encoded by the vaccine.
By the 15-week mark, all of the participants sampled continued to have active germinal centers in their lymph nodes. These centers produced an army of cells trained to remember the spike protein, along with other types of cells, including antibody-producing plasmablasts, that were locked and loaded to neutralize this key protein. In fact, Ellebedy noted that even after the study ended at 15 weeks, he and his team continued to find no signs of germinal center activity slowing down in the lymph nodes of the vaccinated volunteers.
Ellebedy said the immune response observed in his team’s study appears so robust and persistent that he thinks that it could last for years. The researcher based his assessment on the fact that germinal center reactions that persist for several months or longer usually indicate an extremely vigorous immune response that culminates in the production of large numbers of long-lasting immune cells, called memory B cells. Some memory B cells can survive for years or even decades, which gives them the capacity to respond multiple times to the same infectious agent.
This study raises some really important issues for which we still don’t have complete answers: What is the most reliable correlate of immunity from COVID-19 vaccines? Are circulating spike protein antibodies (the easiest to measure) the best indicator? Do we need to know what’s happening in the lymph nodes? What about the T cells that are responsible for cell-mediated immunity?
If you follow the news, you may have seen a bit of a dust-up in the last week on this topic. Pfizer announced the need for a booster shot has become more apparent, based on serum antibodies. Meanwhile, the Food and Drug Administration and Centers for Disease Control and Prevention said such a conclusion would be premature, since vaccine protection looks really good right now, including for the delta variant that has all of us concerned.
We’ve still got a lot more to learn about the immunity generated by the mRNA vaccines. But this study—one of the first in humans to provide direct evidence of germinal center activity after mRNA vaccination—is a good place to continue the discussion.
 SARS-CoV-2 mRNA vaccines induce persistent human germinal centre responses. Turner JS, O’Halloran JA, Kalaidina E, Kim W, Schmitz AJ, Zhou JQ, Lei T, Thapa M, Chen RE, Case JB, Amanat F, Rauseo AM, Haile A, Xie X, Klebert MK, Suessen T, Middleton WD, Shi PY, Krammer F, Teefey SA, Diamond MS, Presti RM, Ellebedy AH. Nature. 2021 Jun 28. [Online ahead of print]
 SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans. Turner JS, Kim W, Kalaidina E, Goss CW, Rauseo AM, Schmitz AJ, Hansen L, Haile A, Klebert MK, Pusic I, O’Halloran JA, Presti RM, Ellebedy AH. Nature. 2021 May 24. [Online ahead of print]
COVID-19 Research (NIH)
Ellebedy Lab (Washington University, St. Louis)
NIH Support: National Institute of Allergy and Infectious Diseases; National Center for Advancing Translational Sciences
Could a Nasal Spray of Designer Antibodies Help to Beat COVID-19?
Posted on by Dr. Francis Collins
There are now several monoclonal antibodies, identical copies of a therapeutic antibody produced in large numbers, that are authorized for the treatment of COVID-19. But in the ongoing effort to beat this terrible pandemic, there’s plenty of room for continued improvements in treating infections with SARS-CoV-2, the virus that causes COVID-19.
With this in mind, I’m pleased to share progress in the development of a specially engineered therapeutic antibody that could be delivered through a nasal spray. Preclinical studies also suggest it may work even better than existing antibody treatments to fight COVID-19, especially now that new SARS-CoV-2 “variants of concern” have become increasingly prevalent.
These findings come from Zhiqiang An, The University of Texas Health Science Center at Houston, and Pei-Yong Shi, The University of Texas Medical Branch at Galveston, and their colleagues. The NIH-supported team recognized that the monoclonal antibodies currently in use all require time-consuming, intravenous infusion at high doses, which has limited their use. Furthermore, because they are delivered through the bloodstream, they aren’t able to reach directly the primary sites of viral infection in the nasal passages and lungs. With the emergence of new SARS-CoV-2 variants, there’s also growing evidence that some of those therapeutic antibodies are becoming less effective in targeting the virus.
Antibodies come in different types. Immunoglobulin G (IgG) antibodies, for example, are most prevalent in the blood and have the potential to confer sustained immunity. Immunoglobulin A (IgA) antibodies are found in tears, mucus, and other bodily secretions where they protect the body’s moist, inner linings, or mucosal surfaces, of the respiratory and gastrointestinal tracts. Immunoglobulin M (IgM) antibodies are also important for protecting mucosal surfaces and are produced first when fighting an infection.
Though IgA and IgM antibodies differ structurally, both can be administered in an inhaled mist. However, monoclonal antibodies now used to treat COVID-19 are of the IgG type, which must be IV infused.
In the new study, the researchers stitched IgG fragments known for their ability to target SARS-CoV-2 together with those rapidly responding IgM antibodies. They found that this engineered IgM antibody, which they call IgM-14, is more than 230 times better than the IgG antibody that they started with in neutralizing SARS-CoV-2.
Importantly, IgM-14 also does a good job of neutralizing SARS-CoV-2 variants of concern. These include the B.1.1.7 “U.K.” variant (now also called Alpha), the P.1 “Brazilian” variant (called Gamma), and the B.1.351 “South African” variant (called Beta). It also works against 21 other variants carrying alterations in the receptor binding domain (RBD) of the virus’ all-important spike protein. This protein, which allows SARS-CoV-2 to infect human cells, is a prime target for antibodies. Many of these alterations are expected to make the virus more resistant to monoclonal IgG antibodies that are now authorized by the FDA for emergency use.
But would it work to protect against coronavirus infection in a living animal? To find out, the researchers tried it in mice. They squirted a single dose of the IgM-14 antibody into the noses of mice either six hours before exposure to SARS-CoV-2 or six hours after infection with either the P.1 or B.1.351 variants.
In all cases, the antibody delivered in this way worked two days later to reduce dramatically the amount of SARS-CoV-2 in the lungs. That’s important because the amount of virus in the respiratory tracts of infected people is closely linked to severe illness and death due to COVID-19. If the new therapeutic antibody is proven safe and effective in people, it suggests it could become an important tool for reducing the severity of COVID-19, or perhaps even preventing infection altogether.
The researchers already have licensed this new antibody to a biotechnology partner called IGM Biosciences, Mountain View, CA, for further development and future testing in a clinical trial. If all goes well, the hope is that we’ll have a safe and effective nasal spray to serve as an extra line of defense in the fight against COVID-19.
 Nasal delivery of an IgM offers broad protection from SARS-CoV-2 variants. Ku Z, Xie X, Hinton PR, Liu X, Ye X, Muruato AE, Ng DC, Biswas S, Zou J, Liu Y, Pandya D, Menachery VD, Rahman S, Cao YA, Deng H, Xiong W, Carlin KB, Liu J, Su H, Haanes EJ, Keyt BA, Zhang N, Carroll SF, Shi PY, An Z. Nature. 2021 Jun 3.
COVID-19 Research (NIH)
Zhiqiang An (The University of Texas Health Science Center at Houston)
Pei-Yong Shi (The University of Texas Medical Branch at Galveston)
IGM Biosciences (Mountain View, CA)
NIH Support: National Institute of Allergy and Infectious Diseases; National Center for Advancing Translational Sciences; National Cancer Institute