Are Vaccinations Given Months Ago Still Preventing Infections
In the absence of a reliable correlate of protection, researchers are looking for signs of waning immunity in real-world data from countries that have advanced vaccination programmes. Are people who were vaccinated early on getting infected at higher rates than those who were vaccinated more recently? Drawing clear conclusions from such data is fraught, says Dvir Aran, a biomedical data scientist at Technion Israel Institute of Technology in Haifa.
Last month, the Ministry of Health in Israel, a country that has one of the worlds highest vaccination rates, released raw data on vaccinations and infections from December 2020 to July 2021. The ministry estimated that vaccine protection against both infection and disease had dropped from above 90% in the early months of its programme to around 40% by late June a decline that could be due to the effects of the Delta variant.
To look more closely for evidence of waning protection, scientists at Kahn Sagol Maccabi in Tel Aviv the research arm of Israeli health-maintenance organization Maccabi Healthcare Services analysed health records from more than 1.3 million people who were vaccinated between January and April 2021. Those vaccinated in January and February were 53% more likely to test positive for SARS-CoV-2 during those four months, compared with people vaccinated in March and April. The differences were even starker among the earliest and latest vaccinated.
Other Immune Processes Are Also Involved
But according to Dr. Stuart P. Weisberg, more research is needed to understand how the immune system responds to SARS-CoV-2 and how long immunity to the virus may last after someone recovers from infection.
Immune protection involves a complex cellular and serological response that cannot be distilled down to production of neutralizing antibodies, Weisberg, an assistant professor of pathology and cell biology at Columbia University Irving Medical Center in New York, New York, said.
In addition to antibody-producing B cells, other types of B cells and T cells also play important roles in warding off viral infections.
For example, memory T cells help the immune system recognize and respond to viruses that its already encountered before.
After viral infection, a small population of long-lived memory T cells remain within the previously infected tissue and continue to circulate throughout the body, Weisberg explained.
These memory cells have the potential to rapidly reactivate upon seeing the virus again, which helps make the second infection less severe than the first, he added
research has found that people whove recovered from COVID-19 do carry SARS-CoV-2-specific T cells. However, more research is needed to learn how much protection those T cells may provide against reinfection.
Natural Infection Versus Vaccination: Differences In Covid Antibody Responses Emerge
Colored transmission electron micrograph of SARS-CoV-2 coronavirus particles. Credit: National Infection Service/SCI.
This news story has been updated to reflect the publication of the study, previously available on BioRxiv, in a peer-reviewed journal.
Hope for a future without fear of COVID-19 comes down to circulating antibodies and memory B cells. Unlike circulating antibodies, which peak soon after vaccination or infection only to fade a few months later, memory B cells can stick around to prevent severe disease for decades. And they evolve over time, learning to produce successively more potent memory antibodies that are better at neutralizing the virus and more capable of adapting to variants.
Vaccination produces greater amounts of circulating antibodies than natural infection. But a new study suggests that not all memory B cells are created equal. While vaccination gives rise to memory B cells that evolve over a few weeks, natural infection births memory B cells that continue to evolve over several months, producing highly potent antibodies adept at eliminating even viral variants.
The findings highlight an advantage bestowed by natural infection rather than vaccination, but the authors caution that the benefits of stronger memory B cells do not outweigh the risk of disability and death from COVID-19.
Your body on COVID-19
The convalescent advantage
To boost or not to boost
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Is There Any Difference In Vaccine Induced Immunity Between The First And Second Doses
Its difficult to get a sense of the entire immune response after one dose of vaccine versus two, but multiple studies have investigated antibody levels at different stages of dosing. One preprint study from researchers at University College London involving more than 50 000 participants found that 96.4% were antibody positive one month after their first dose of either the Pfizer or AstraZeneca vaccines, and 99.1% were antibody positive between seven and 14 days after their second dose.15 Median antibody levels changed slightly up to two weeks after the second dose, at which point they rocketed.
Another study, also a preprint by researchers in the UK, evaluated the difference in peak antibody levels among 172 people over 80 who received the Pfizer vaccine.16 Those who had no previous record of covid-19 infection had 3.5 times more antibodies at their peak if they received their second dose 12 weeks later rather than three weeks later. However, median T cell levels were 3.6 times lower in those who had the longer dosage interval . This again shows how early we are in our understanding of the virus and immunity to it.
Covid: Antibodies Last At Least Six Months In Most
As many as 88% of people still have antibodies in their blood to fight Covid-19 six months after infection, a study of almost 1,700 people suggests.
The data – from one of the world’s largest follow-up Covid studies – also provides more detail about the likely symptoms experienced by those infected.
While 26% had a cough and 28% had a fever, a bigger proportion – 43% – said they lost the sense of taste or smell.
But 40% had had none of these – and about 20% had had no symptoms at all.
The data also backs up previous studies on who is most likely to have been infected with Covid at some point during the pandemic.
Among a full group of nearly 20,000 people who were regularly tested monthly during the pandemic, it was younger adults, black or South Asian people and those living in deprived areas who were most likely to test positive for the antibodies.
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What You Should Know
- Antibody tests use a sample of your blood to check for antibodies. Your body makes antibodies after it’s infected by a virus or other infectious agents, or after you receive a vaccination.
- It takes time for your body to make antibodies. They usually start to appear in your blood 7 to 10 days after your initial infection or after your vaccination.
- Vaccination is one of the most effective ways to prevent the spread and reduce the impact of an infectious disease.
- The antibodies that may be produced after infection with SARS-CoV-2 will not necessarily protect you from getting sick again and it’s not known how long they will remain in your body.
Regardless of your test result, you must continue to follow public health guidelines to reduce the risk of infection and transmission.
How Soon After Covid
How soon is too soon to get vaccinated after you’re sick with COVID-19? If you’re no longer sick and out of isolation, you should get vaccinated.
We recommend that people with post-COVID syndrome should get the vaccine as well. There are some reports of people with post-COVID syndrome experiencing marked improvement in symptoms following vaccination.
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What It Will Take To Vaccinate The World Against Covid
Within just a few months, pharmaceutical firms have produced hundreds of millions of doses of COVID-19 vaccine. But the world needs billions and as fast as possible. Companies say they could make enough vaccines to immunize most of the worlds population by the end of 2021. But this doesnt take into account politically based delays in distribution, such as countries imposing export controls or that the overwhelming majority of doses are going to wealthier countries. This situation is fuelling a campaign to temporarily waive intellectual-property rights so that manufacturers in poorer countries can make the vaccines more quickly themselves.
Natural Immunity Alone Is Weak
One study compared natural immunity alone to natural immunity plus vaccination. They found that, after infection, unvaccinated people are 2.34 times likelier to get COVID-19 again, compared to fully vaccinated people. So vaccinated people have half the risk of reinfection than people relying on natural immunity alone.
“Studies show that the vaccine gives a very good booster response if you’ve had COVID-19 before,” says Dr. Rupp.
Furthermore, there is no country on the globe in which natural infection and natural immunity has brought the pandemic under control. In countries like Iran or Brazil very high levels of natural infection have not prevented recurrent waves of infection.
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What About T And B Cell Responses
T and B cells have a central role in fighting off infections and, crucially, in establishing long term immunity. Some T and B cells act as memory cells, persisting for years or decades, primed and ready to reignite a broader immune response should their target pathogen arrive in the body again. Its these cells that make truly long term immunity possible.
A study published in February in Science assessed the proliferation of antibodies as well as T and B cells in 188 people who had had covid-19.7 Although antibody titres fell, memory T and B cells were present up to eight months after infection. Another study in a comparably sized cohort reported similar results in a preprint posted to MedRxiv on 27 April.8
Monica Gandhi, an infectious disease doctor and professor of medicine at the University of California San Francisco, says we have evidence that T and B cells can confer lifelong protection against certain diseases similar to covid-19. A well known Nature paper from 2008 found that 32 people born in 1915 or earlier still retained some level of immunity against the 1918 flu strain, 90 years hence.9 That is really profound, she says.
A Third Of Infections Don’t Get Any Protective Antibodies
Some people who get COVID-19 receive no protection from reinfection their natural immunity is nonexistent. A recent study found that 36% of COVID-19 cases didn’t result in development of SARS-CoV-2 antibodies. The people had different levels of illness most had moderate disease, but some were asymptomatic and some experienced severe COVID-19.
“Vaccine-induced immunity is more predictable than natural immunity,” says Dr. Rupp. The COVID-19 vaccines provide great protection from severe disease, hospitalization and death.
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Follow Public Health Advice To Slow The Spread Of Covid
Even if you have previously had a COVID-19 infection or vaccination, you must still follow public health advice. You must take the same actions to prevent COVID-19 as someone who has never had the infection or the vaccine:
- Wash your hands often with soap and water for at least 20 seconds.
- If soap and water aren’t available, use a hand sanitizer containing at least 60% alcohol.
- Stay home as much as possible and if you need to leave the house, practise physical distancing .
- Wear a non-medical mask or face covering to protect others when you can’t maintain a 2-metre distance.
- Avoid close contact with people who are sick.
- Cough and sneeze into your sleeve and not your hands.
- Follow the advice of your local public health authority.
Please contact your health care provider with any questions or concerns about your test.
For more information on COVID-19: 1-833-784-4397 Canada.ca/coronavirus
To What Extent Is Intellectual
Some 11 billion doses are required to vaccinate 70% of the world’s population assuming two doses are given per person. This is the proportion that might be needed to reach population-level, or herd, immunity.
According to researchers at Dukes Global Health Innovation Center, high- and upper-middle-income countries, representing one-fifth of the worlds population, have bought around 6 billion doses but low- and lower-middle-income countries, representing four-fifths of the population, have secured only around 2.6 billion. This includes 1.1 billion doses for COVAX, a scheme in which international funders have pledged to vaccinate one-fifth of the worlds population. By this measure, the researchers say, it could take two or more years for people in the lowest-income groups to be vaccinated.
Thats why India and South Africa are among the countries involved in a campaign to get COVID-19-related intellectual-property rights temporarily waived. This, the campaign’s proponents argue, will unleash a cascade of production.
The proposal was discussed at a WTO meeting on 10 and 11 March, and talks are due to resume next month. Proponents argue that the waiver will enable governments and manufacturers to jointly organize a ramping up of vaccine supply. Without such a waiver, they say, poorer countries will remain dependent on the charity of richer countries and their pharmaceutical industries.
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What Other Types Of Tech Transfer Could Speed Up Vaccine Production
The WHO is advocating what it calls coordinated technology transfer, in which universities and manufacturers license their vaccines to other companies through a global mechanism coordinated by the WHO, which would also facilitate the training of staff at the recipient companies, and coordinate investments in infrastructure. It says this approach is more coherent and transparent than one-off tech-transfer deals such as that between AstraZeneca and Serum Institute.
In another approach, the University of Pennsylvania, which owns sufficient intellectual-property rights relating to mRNA vaccines to strike out on its own, is helping Chulalongkorn University in Bangkok to develop a vaccine-making facility.
If you look at vaccine roll-out right now, its going to be two years before Thailand and other lower-income countries get vaccine, says Weissman, who is collaborating on the project. The countrys government wasnt willing to wait, he says. They were willing to put up the money so that theyll be ready to treat their people by the end of this year.
In the long term, argues Friede, every region needs a facility that fully owns the production know-how and can produce vaccines. The gap is most egregious in Africa, a continent that imports 99% of its vaccines, says Nkengasong. It has only three big vaccine manufacturers.
Weaknesses Of The Study
Scientists who spoke to the Science Media Centre in London highlighted several shortcomings of the study, which has not been published either as a preprint or peer-reviewed paper.
These results are rather simplistic and incomplete, said Dr. Julian Tang, professor of respiratory sciences at the University of Leicester in the U.K.
He pointed out that the study did not measure the responses of participants T cells, which play a vital role in the bodys adaptive immune system alongside B cells, which produce antibodies.
T cell responses have been investigated previously and can offer immune protection even in the absence of an antibody response or symptomatic infection, he said.
In addition, he said the study did not measure a class of antibodies known as IgA within mucous membranes. These are a first line of defense against infection in the respiratory tract.
Dr. Tang also cited a study , which found that individuals vary widely in the timing of their antibody responses to infection with SARS-CoV-2 from 033 days from onset of symptoms.
While not specifically a study relating to anti-N antibody levels, it is possible that the timing of the sample may have affected the findings of the ZOE study. They only tested a single sample from each participant over a period of at least 9 months from symptom onset.
Finally, he pointed out that the ZOE study did not test for the presence of antibodies against other proteins in the virus.
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‘i Am Broken And My Colleagues Are Broken: ‘ Montana Icu Nurse As Covid
Dr. Anthony Fauci, the nations top infectious disease expert, echoed that sentiment, adding that declining antibody levels do not necessarily translate into a lack of immunity.
Just because the level of antibodies diminish, that doesnt mean you lose protection, he said Thursday in a press briefing from the National Institutes of Health.
In the recent study published in Science, researchers at the Icahn School of Medicine at Mount Sinai used a database of immune responses from 30,000 New Yorkers who tested positive for the coronavirus between March and October and monitored 121 volunteers over time.
The researchers found that antibody responses peaked roughly two to three months after infection. And in 90 percent of the people who recovered, antibody levels subsequently dropped but remained stable for around five months, said Dr. Ania Wajnberg, an associate professor of medicine at the Icahn School of Medicine and a co-author of the Mount Sinai study.
A majority of patients have a relatively robust response and so far, that is persisting over time, she said.
In the U.K. study, scientists at Imperial College London found that antibody prevalence in the British participants fell from 6 percent at roughly the end of June to 4.4 percent in September. And using at-home tests that were distributed to more than 365,000 people, the researchers observed a more than 26 percent decline in antibody levels over three months.
Antibody Testing Can Help Combat Coronavirus
Once accurate antibody testing becomes widely available, it may help limit the spread of the novel coronavirus.
Accurate results will indicate how many people have recovered from COVID-19, even if they did not have symptoms. This may help determine who has some level of immunity to the virus.
Accurate test results can also help with contact tracing of people who have interacted with those with the virus.
Determination of the overall spread of the disease will also be possible with antibody testing.
Another benefit is that people who have had COVID-19 may be able to donate plasma that contains antibodies to the virus. The plasma may help treat people with severe COVID-19 disease. This treatment is known as convalescent plasma therapy.
There are some limitations of COVID-19 antibody testing. According to the American Society for Microbiology, antibody testing:
- cannot definitively determine if a person has immunity
- cannot determine current or very recent cases of COVID-19
- must not inform a personâs physical distancing, hygiene practices, or personal protective equipment use
Similarly, the CDC advise that antibody test results should not determine when people can return to work or mix with others. Neither should it affect when they can group together in schools, correctional facilities, and other settings.
These limitations may reduce once more accurate and widespread testing becomes available, and researchers have carried out more studies.
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