Reduction of antibodies ‘three months after natural infection’ could mean very little…

The second phase of the national serologic inquiry was reported this week as having “sounded the alert to the reduction of antibodies against SARS-CoV-2 just three months after infection” (click here).

Said INSA (the national health institute Dr Ricardo Jorge) this is why people who have been previously infected need to be vaccinated.

This part of the message however may have been a little skewed. 

Further down within INSA’s statement came the assertion that “an absence of antibodies may not mean that people are vulnerable”.

In the meantime, DGS health authorities have already said that people infected naturally with the virus should sign-up for vaccines using the self-scheduling platform from June if they have recovered from the virus more than six months ago.

Again, studies coming out of the United States many months ago suggest this might not be necessary (see below).

The direction of texts in the Portuguese press however was that people infected naturally with Covid-19 may have a lower level of antibodies present in the months following infection than those who have been vaccinated.

Said INSA’s document: “Our results suggest that individuals infected with SARS-CoV-2 have lower levels of antibodies than vaccinated (people), similar to results obtained in clinical trials (…). Whatever the case these results support the option of vaccinating people previously infected with SARS-CoV-2”.

But is it that simple?

A study carried out in Israel (where vaccination roll-out has been ‘the most comprehensive in the world’) showed that Covid antibody levels also decline significantly two months after injection of the second dose of the coronavirus vaccine.

In other words, the focus on ‘antibodies’ (whether people caught the virus naturally or have been vaccinated) may be spurious.

Explain reports from Israel, “according to a study which focused on staff members at Sheba Medical Center in Tel HaShomer, in Ramat Gan, serum antibody levels appeared to drop off roughly two months after the second dose of the Pfizer vaccine, potentially raising questions about the long-term efficacy of the vaccine and the possibility that additional doses may be required to maintain immunity.

“But some experts say the study is not necessarily cause for alarm, noting that similar declines are observed with antibodies for other viruses, and that antibodies make up only part of the body’s immune system.

“Antibody levels aren’t the only indicator of the level of immunity,” said Dr. Orly Greenfield, outgoing medical director for the Magen Yisrael program.

“In an interview with Israel’s Channel 12, Dr. Greenfield said the long-term effectiveness of the vaccine remains unknown, but added that there is no reason to believe the decline in antibodies indicates a loss of immunity.

“We still don’t know how effective the vaccine is, but we do know that as is the case with other vaccines, sometimes there is a drop in the quantity of antibodies after a certain period.”

“While antibodies have received much attention in public discussions of the COVID vaccine, they make up only one part of the immune system, Greenfield emphasized.

“The body’s immune system is made up of multiple things – there are antibodies but also cell-mediated immunity; that is, cells which envelope viruses. That remains for the long-term. So these things still need to be studied, and we’re constantly following up and checking.

“It is possible that while the antibody levels fall, we still have full immunity, like we had before,” he said.

US study ‘hints’ that immunity to SARS-CoV-2 “could last years”

This is another study that INSA’s research, and message, seems to have missed. 

Reported in the New York Times last November, it concluded that “eight months after (natural) infection, most people who have recovered still have enough immune cells to fend off the virus and prevent illness. A slow rate of decline in the short term suggests, happily, that these cells may persist in the body for a very, very long time to come”.

Back in November the research had not been peer-reviewed or published in a scientific journal, but it was “the most comprehensive and long-ranging study of immune memory to the coronavirus to date”, said the NYT.

And according to Professor Shane Crotty, the virologist who co-led the study out of the La Jolla Institute of Immunology: “That amount of memory would likely prevent the vast majority of people from getting hospitalised disease, severe disease, for many years”.

The NYT adds that the La Jolla research “squares with another recent finding: that survivors of SARS, caused by another coronavirus, still carry certain important immune cells 17 years after recovering”.

The article (click here) refers to other studies carried out by laboratories: all of them conceding that the immune response from Covid-19 essentially follows that of other coronaviruses and is long-lasting.

Now the big question is ‘will the immune response from the vaccines be the same?’.

La Jolla research assistant Daniella Weiskopf told online science news service EurekAlert! earlier this year that the fact that immune memory against SARS-CoV-2 is possible is “a good sign”.

“It is possible that immune memory will be similarly long lasting following vaccination, but we will have to wait until the data come in to be able to tell for sure,” she said. “Several months ago, our studies showed that natural infection induced a strong response, and this study now shows that the response lasts. The vaccine studies are at the initial stages, and so far have been associated with strong protection. We are hopeful that a similar pattern of responses lasting over time will also emerge for the vaccine-induced responses”.

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