If you’ve already had COVID, do you need a vaccine?


The Seattle Times 12 October, 2021 - 07:22am 5 views

Nationwide study shows link between COVID vaccination and reduced household transmission in Sweden

Medical Xpress 12 October, 2021 - 11:20am

GENEVA: The World Health Organisation has recommended that people with a weaker immunity system should be given an additional dose of COVID-19 vaccine, due to their higher risk of breakthrough infections after standard immunisation.

The Strategic Advisory Group of Experts on Immunisation said the additional dose should be offered "as part of an extended primary series since these individuals are less likely to respond adequately to vaccination following a standard primary vaccine series and are at high risk of severe COVID-19 disease".

WHO vaccine director Kate O'Brien, referring to people with lower immunity due to other conditions, told a news briefing: "The recommendation is for a third vaccination, an additional vaccination in the primary series and again that is based on the evidence showing that the immunogenicity and evidence on breakthrough infections is highly disproportionately represented by those people."

The panel also recommended that people over 60 receive an additional dose of the shots made by Chinese vaccine makers Sinopharm and Sinovac some one to three months after completing their schedule, citing evidence in studies in Latin America that they perform less well over time.

Observational data on Sinopharm and Sinovac shots "clearly showed that in older age groups ... the vaccine performs less well after two doses", said Joachim Hombach, secretary of the independent panel of experts who held a five-day closed-door meeting last week.

"We also know that the addition of a third dose or moving into a two-plus-one schedule provides a strong (immune) response. So we expect from there a much better protection," he said.

Health authorities using the Sinopharm and Sinovac vaccines should aim first to maximise two-dose coverage in the older populations and then administer the third dose, the panel said.

The SAGE group, composed of independent experts who make policy but not regulatory recommendations, will review all global data on booster shots in a November 11 meeting, amid questions over variants and potential waning of immunity, O'Brien said.

Currently some 3.5 billion doses of COVID-19 vaccines have been administered, O'Brien said.

An estimated 1.5 billion doses are available globally each month, enough to meet the target of vaccinating 40% of each country's population by year-end, but distribution is unequal, she added.

"Giving those booster doses to individuals who have already had the benefit of a primary response is like putting two life jackets on somebody and leaving others without any lifejacket," O'Brien said.

"In this sense we are talking about getting the first lifejacket onto people who have immunocompromising conditions."

Do people who have had Covid-19 really need the vaccine? Here's what experts say

Economic Times 12 October, 2021 - 04:46am

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Covid-19 Vaccination Linked with Reduced Household Transmission: Study

News18 12 October, 2021 - 04:40am

The research, published in the journal JAMA Internal Medicine, found that there was a dose-response association between the number of immune individuals in each family and the risk of infection and hospitalisation in non-immune family members.

Non-immune family members had a 45 to 97 per cent lower risk of infection and hospitalisation, as the number of immune family members increased, the researchers said.

“The results strongly suggest that vaccination is important not only for individual protection but also for reducing transmission, especially within families, which is a high-risk environment for transmission," said Peter Nordstrom, a professor at Umea University in Sweden. The researchers noted that there is a vast body of research showing that vaccines strongly reduce the risk of COVID-19.

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However, less is known about the influence of vaccination on transmission of the virus in high-risk environments, such as within families, they said. The latest research is a nationwide, registry-based study of over 1.8 million individuals from more than 800,000 families.

The researchers’ combined registry data from the Public Health Agency of Sweden, the National Board of Health and Welfare, and Statistics Sweden, which is the government agency that oversees statistical data.

They quantified the association between the number of family members with immunity against Covid-19 and the risk of infection and hospitalisation in non-immune individuals.

The study accounted for differences in age, socioeconomic status, clustering within families, and several diagnoses previously identified as risk factors for Covid-19 in the Swedish population.

The researchers noted that it appears that vaccination helps not only to reduce the individual’s risk of becoming infected but also to lower transmission.

This “in turn minimises not only the risk that more people become critically ill, but also that new problematic variants emerge and start to take over," said Marcel Ballin, a doctoral student at Umea University.

“Consequently, ensuring that many people are vaccinated has implications on a local, national, and global scale," Ballin, co-author of the study, added.

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If You’ve Had Covid, Do You Need the Vaccine?

ANC 24/7 12 October, 2021 - 01:30am

So-called natural immunity varies from patient to patient, scientists say. Immunization is still the best choice after recovering from the disease.

When Jonathan Isaac, a prominent basketball player for the Orlando Magic, explained why he chose not to be vaccinated against the coronavirus, he tapped into a dispute that has been simmering for months: Do people who have had Covid-19, as Mr. Isaac said he has, really need the vaccine?

That question has thrust tortuous immunological concepts into a national debate on vaccine mandates, with politicians, athletes, law professors and psychiatrists weighing in on the relative strength of so-called natural immunity versus the protection afforded by vaccines.

But the answer, like nearly everything about the virus, is complicated.

While many people who have recovered from Covid-19 may emerge relatively unscathed from a second encounter with the virus, the strength and durability of their immunity depends on their age, health status and severity of initial infection.

“That’s the thing with natural infection — you can be on the very low end of that or very high end, depending on what kind of disease you developed,” said Akiko Iwasaki, an immunologist at Yale University.

Those with powerful natural immunity may be protected from reinfection for up to a year. But even they should not skip the vaccine, experts said. For starters, boosting their immunity with a vaccine is likely to give them long-lasting protection against all the variants.

“If you’ve gotten the infection and then you’ve been vaccinated, you’ve got superpowers,” said Jennifer Gommerman, an immunologist at the University of Toronto.

Without that boost, antibodies from an infection will wane, leaving Covid-recovered people vulnerable to reinfection and mild illness with variants — and perhaps liable to spread the virus to others.

This is the same argument for giving boosters to people who are fully vaccinated, said Michel Nussenzweig, an immunologist at Rockefeller University in New York. “After a certain period of time, you’re either going to get boosted or you’re going to get infected,” he said.

How immunity from infection and from vaccination compare is difficult to parse. Dozens of studies have delved into the debate, and have drawn contradictory conclusions.

Some consistent patterns have emerged: Two doses of an mRNA vaccine produce more antibodies, and more reliably, than an infection with the coronavirus does. But the antibodies from prior infection are more diverse, capable of fending off a wider range of variants, than those produced by vaccines.

Studies touting the durability and strength of natural immunity are hobbled by one crucial flaw. They are, by definition, assessing the responses only of people who survived Covid-19. The road to natural immunity is perilous and uncertain, Dr. Nussenzweig said.

Only 85 percent to 90 percent of people who test positive for the virus and recover have detectable antibodies to begin with. The strength and durability of the response is variable.

For example, while the immunity gained from vaccines and infection is comparable among younger people, two doses of the mRNA vaccines protected adults older than 65 better than a prior infection did.

Research published by Dr. Iwasaki’s team in May showed a stepwise increase in the level of antibodies with rising severity of infection. About 43 percent of recovered people had no detectable neutralizing antibodies — the kind needed to prevent reinfection — according to one study. The antibodies drop to undetectable levels after about two months in about 30 percent of people who recover.

Other researchers may find different results depending on the severity of illness in the participants, said Fikadu Tafesse, an immunologist at Oregon Health & Science University.

“If your cohort is just only hospitalized individuals, I think the chance of having a detectable antibody is higher,” Dr. Tafesse said.

In terms of the quality of the antibodies, it makes sense that invasion by a live virus would produce a broader immune response than would injecting the single protein encoded in the vaccines, he and others said.

The virus would stimulate defenses in the nose and throat — exactly where they are needed to prevent a second infection — while the vaccines produce antibodies mainly in the blood.

“That will give you an edge in terms of resisting a subsequent infection,” Dr. Gommerman said.

Fragments of the virus may also persist in the body for weeks after infection, which gives the immune system more time to learn to fight it, while the proteins carried by the vaccine quickly exit the body.

Several studies have now shown that reinfections, at least with the earlier versions of the virus, are rare.

At the Cleveland Clinic, none of 1,359 health care workers who remained unvaccinated after having Covid-19 tested positive for the virus over many months, noted Dr. Nabin Shrestha, an infectious disease physician at the clinic.

But the findings must be interpreted with caution, he acknowledged. The clinic tested only people who were visibly ill, and may have missed reinfections that did not produce symptoms. The participants were 39 years old on average, so the results may not apply to older adults, who would be more likely to become infected again.

Most studies have also tracked people for only about a year, Dr. Shrestha noted. “The important question is, how long does it protect, because we’re not under any illusions that this will be a lifelong protection,” he said.

It’s also unclear how well immunity after infection protects against the newer variants. Most studies ended before the Delta variant became dominant, and more recent research is patchy.

The most widely cited study in favor of natural immunity’s potency against the Delta variant comes from Israel.

Breakthrough infections after vaccination were 13-fold more likely than reinfections in unvaccinated people, and symptomatic breakthrough infections 27-fold more likely than symptomatic reinfections, the study found.

But experts cautioned against inferring from the results that natural immunity is superior to the protection from vaccines. The vaccinated group included many more people with conditions that would weaken their immune response, and they would be expected to have more breakthrough infections, noted Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health.

The study also did not account for people whose immune defenses may have been strengthened by a second exposure to the virus.

For those lucky enough to have recovered from Covid-19, vaccination is still the ideal choice, experts said. It provides a massive boost in antibody levels and a near-impenetrable immune shield — perhaps even against future variants.

“They are like rock stars on all the variants,” said Dr. Duane Wesemann, an immunologist at Harvard Medical School.

Colorful graphs from Dr. Wesemann’s recent paper have been helpful for convincing Covid-recovered patients of the stark advantage even a single dose would offer them, he said.

Regardless of the evolving understanding of natural immunity, on one point there is near-universal agreement among scientists. For people who were never infected, vaccines are much safer, and far less a gamble, than Covid-19.

Many people who argue against vaccines cite the low mortality rates from Covid-19 among young people. But even seemingly mild cases of Covid-19 can result in long-term damage to the heart, kidneys and brain, or leave people feeling exhausted and unwell for weeks to months, Dr. Iwasaki said.

“No one should try to acquire immunity through natural infection,” she said. “It’s just too dangerous.”

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