Vaccination protection continues to be safest option compared to dependence on antibodies alone

Exposure to Covid-19 provides some future protection but vaccines remain crucial.

A recent study by the US Centers for Disease Control and Prevention (CDC) found that people who had previously contracted Covid-19 were better protected against the Delta variant than those who had been vaccinated without prior infection, but experts have warned against using the data, which comes with many caveats, to cast doubt on the need to get vaccinated and question vaccine mandates.

In its report, released on 28 January 2022, the CDC analysed data from 1.1 million cases in California and New York, breaking them up into four groups: those who have been vaccinated and have had prior infection; those who have been vaccinated without prior infection; those who have had Covid but not been vaccinated; and those who have neither had Covid nor been vaccinated.

People who have been vaccinated and have had a prior Covid-19 case still have the most protection against infection and severe disease. Those who have not been vaccinated and haven’t been exposed to the virus are the most vulnerable.

“The evidence in this report does not change our vaccination recommendations,” the CDC’s Dr Ben Silk told a media briefing. “We know that vaccination is still the safest way to protect yourself against Covid-19.”

Prior to the Delta variant, people who had been vaccinated but had not contracted Covid had more protection than those who had survived Covid without being vaccinated. According to the new study, that flipped during the Delta variant.

“Importantly, infection-derived protection was greater after the highly transmissible Delta variant became predominant, coinciding with early declining of vaccine-induced immunity in many persons,” said the CDC report.

In a video with almost two million views, YouTuber John Campbell, who describes himself as a retired nursing teacher with a PhD, used the data to suggest it’s not necessary to get vaccinated if you have already had Covid. In the US, the study has been used to question the need for vaccine mandates and call for the recognition of infection-derived protection in pandemic regulations.

The CDC’s report, however, identifies seven limitations of its study. It didn’t take into account the time since someone was vaccinated and the severity of symptoms after someone was initially exposed to Covid. It was conducted before the widespread roll-out of booster shots and the emergence of the Omicron variant.

Professor Shabir Madhi, dean of the faculty of health sciences and a professor of vaccinology at the University of the Witwatersrand, said: “Vaccines still have a role to play in people who have past infection, as have a broader repertoire of immune responses that likely protects better than infection alone against severe Covid.

“Also, this hybrid immunity (including if vaccine preceded infection) results in much higher neutralising antibody responses … which [are] able to overcome much of antibody evasiveness of even Omicron.”

He warned of the consequences of people believing that they will continue to be protected after contracting Covid-19 and choosing not to get vaccinated. “[It] will result in future resurgences that are higher than would otherwise have occurred, and also leaves people less protected against mild Covid, and … high-risk groups also remain at higher risk of severe Covid than someone who is vaccinated and was infected (in either order).” Dr Peter Chin-Hong, an infectious disease expert at the University of California, San Francisco, pointed out the flaws in choosing to ignore vaccination. “There is not enough precision to say whether recent infection is ‘better’ than getting vaccinated and it all depends on what you consider to be success. As an infectious disease physician who has taken care of hundreds of Covid patients over the past two years in the hospital, prevention of serious disease is paramount: not prevention of infection as the main metric,” he said.

“The idea of getting naturally infected as a substitute for vaccination is inherently flawed and much more unsafe as a strategy. Getting naturally infected is no walk in the park: there is the risk of getting very ill, hospitalised, needing mechanical ventilation in the ICU and dying,” he said.

“There are many additional complications that arise from Covid: blood clots and myocarditis that are much more likely to arise in the case of Covid than vaccinations, as well as numerous other complications from Covid, like foetal demise. Also, a hospital visit comes with numerous other non-Covid risks such as hospital-acquired infections. After survival from Covid, the risk of chronic complications or ‘long Covid’ is not insignificant and clearly more common in natural infection versus vaccination.”

Chin-Hong said the CDC’s study was a snapshot in time that didn’t explain how long immunity from previous infection would last and didn’t take booster shots into account.

“Relying on one bout of natural infection is as foolhardy as relying on one shot only to protect against future infection and disease. It is not the nature of the insult but rather how many times the immune system is reminded that gives the best insurance against future variants and the outcomes we care most about: hospitalisation and death,” Chin-Hong continued.

He expects that over time the immunity protection from prior Covid-19 cases will wane faster than immunity from the vaccination “and the people left standing will be those who would have received boosters”. “Because of this, not getting vaccinated could prolong the pandemic and result in continued transmission events and stretch our hospital resources further.”

Chin-Hong said that protection as a result of recent prior infection could be considered in vaccine mandates in the short term but not when looking at long-term robust immunity. Madhi said there is still a strong case for vaccine mandates. Both experts and the CDC data are clear: as the pandemic continues and new variants emerge, vaccination remains the safest way to protect yourself from Covid-19. DM168

This story first appeared in our weekly Daily Maverick 168 newspaper which is available for R25 at Pick n Pay, Exclusive Books and airport bookstores. For your nearest stockist, please click here.

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"Information pertaining to Covid-19, vaccines, how to control the spread of the virus and potential treatments is ever-changing. Under the South African Disaster Management Act Regulation 11(5)(c) it is prohibited to publish information through any medium with the intention to deceive people on government measures to address COVID-19. We are therefore disabling the comment section on this article in order to protect both the commenting member and ourselves from potential liability. Should you have additional information that you think we should know, please email [email protected]"

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