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HomeMedical AnalysisWhy you’ll need COVID boosters repeatedly, like flu jabs – Yale experts

Why you’ll need COVID boosters repeatedly, like flu jabs – Yale experts

As the effectiveness of a primary series of mRNA vaccines, shown to have high efficacy rates, to prevent hospitalisation and death is also being chipped away by highly immune-evasive coronavirus variants, boosters are becoming increasingly important, say scientists.

Several highly effective vaccines were developed at an unprecedented speed to combat the COVID-19 pandemic, and during the phase three clinical trials, mRNA vaccines had vaccine efficacy of 94–95% in preventing symptomatic infections.

After the roll-out, real-world evidence showed that the mRNA vaccines provided 90% effectiveness against infection. Then came the variants. The wave after wave of new variants, with ever-increasing transmissibility and capacity to escape existing immunity, challenged the ability of vaccines to prevent infection and transmission.

Writing in TIME, professors and epidemiological specialists Akiko Iwasaki and Albert Ko from Yale University say that the effectiveness of a primary series of mRNA vaccines (two doses) to prevent hospitalisation and death is also being chipped away by these highly immune-evasive variants.

Vaccine-mediated protection became shorter-lived, they write, especially with the emergence of Omicron variants. People look at these data and wonder what is the point of getting the vaccines if they will not prevent symptomatic infections, and the protection does not last?

Well, to expect robust protection from just the primary series of any vaccines is unreasonable – and was always likely to be – but somehow society has placed too high a bar on what is considered an acceptable number of doses for COVID-19 vaccines. Instead, we need to understand that we’re going to be getting boosters in the foreseeable future, and to appreciate their benefits.

Vaccines against other infectious diseases are given in multiple doses. Many of our childhood vaccines require multiple doses: five doses for (diphtheria/tetanus/pertussis), four doses (Haemophilus influenza type b, pneumococcal conjugate, inactivated poliovirus), or three doses (hepatitis B) are all commonly given before the age of 18. These doses are required and not considered optional to achieve immunity.

In adulthood, many of these vaccines need periodic booster doses to maintain immunity. The influenza virus requires annual vaccination doses for all ages. Yet, people don’t complain about having to get their 60th dose of the influenza vaccine.

We should think of COVID-19 vaccines the same way.

Why do we need booster doses? The primary series of vaccines kickstarts the immune response by engaging lymphocytes, white blood cells that detect specific features of the pathogen to expand in numbers and become instructed to eliminate the pathogen.

Most of these cells disappear over time, except for a small subset of cells retained by the body for future use. These “memory cells” are responsible for long-lasting immunity against a given pathogen. What boosters do is stimulate these memory lymphocytes to quickly expand in numbers and to produce even more effective defenders.

The booster also selects for B cells that can secrete antibodies that are even better at binding and blocking virus infection and spread.

The primary series can be thought of as the high school for lymphocytes, where naïve cells receive basic instructions to learn about the pathogen. Boosters are like a college where lymphocytes are further educated to become more skilled and mature, to fight off future infections. Periodically, these college graduates need refreshers by more booster doses given later in life. This is the case for all vaccines. Booster doses provide the immune system the education it needs to prevent severe diseases from infections.

COVID-19 vaccines also need booster doses for the same reasons. We need to educate, maintain, and improve T and B cell responses to prevent severe disease.

Boosters provide significant benefits to people who received the primary series in preventing hospitalisation and death. In the US in April 2022, people over 50 who received no vaccine, primary series only (no booster dose), or one booster dose, had 38x, 6x, or a 4x higher risk, respectively, of dying from COVID-19 compared with those with two or more booster doses. During the Omicron-predominant period, the booster dose provided protection from hospitalisation even in previously infected people, whether older (>65 years of age) or younger (<65 years of age).

Among children and adolescents, a primary series (two doses) of vaccination was less effective in preventing COVID-19-associated emergency department and urgent care encounters during the Omicron wave compared with the Delta period. Immunity also decreases with time since primary vaccination. No significant protection was detected more than five months after a second vaccine dose among adolescents aged 16–17 years.

However, a third booster dose restored vaccine effectiveness to 81% in this age group. There is thus a clear benefit of a booster dose across a broad range of age groups studied to date.

Can booster vaccination be improved in the future? Absolutely. We need improved boosters that can provide more durable protection, are effective against variants we encounter moving forward, and do a better job of preventing infection and blocking transmission.

For example, booster-induced immune protection wanes within four to six months during the current Omicron period. We need vaccine strategies that provide more durable protection. Boosters are now being developed to match the circulating Omicron variant BA.5, which should provide better protection than boosters based on the original strain.

However, because of the rapidly mutating nature of SARS-CoV-2, in the future, we will need boosters that can provide coverage against not just the existing but future variants of concern.

Boosters that work against a wide range of SARS-CoV-2 variants, now or in the future, as well as against other coronaviruses that may cause future pandemics, must be pursued.

Coronaviruses have made the jump from animals to humans multiple times in history, which resulted in pandemics. Vaccines that can broadly protect against a wide range of coronaviruses will also prevent future pandemics. In addition, future boosters should be given as nasal spray vaccines to provide local mucosal immune protection, capable of reducing infection and transmission at the portal of entry for the virus, and reducing long COVID risk.

Ultimately, we need booster strategies that can be more easily implemented worldwide and have higher acceptance and uptake rates to provide much-needed immune protection for everyone. An over-the-counter nasal spray booster can bring us closer to that goal.

Researchers and industry are furiously working on developing next-generation vaccines as they did with our current vaccines, which have saved more than 14m lives during the pandemic.

But for now, take the booster doses for which you are eligible to keep your immune system educated and up to date so it has the best chance of protecting you from COVID-19 and to help prevent the enormous loss of life we experienced last winter with more than 300,000 people dying in the US from a disease that can be prevented by current boosters.

Iwasaki is the Sterling Professor of Immunobiology and Professor of Dermatology and of Molecular, Cellular, and Developmental Biology and of Epidemiology at Yale University School of Medicine

Ko is the Raj and Indra Nooyi Professor of Public Health and Professor of Epidemiology (Microbial Diseases) and of Medicine (Infectious Diseases) at Yale University School of Medicine

 

TIME article – Why You’ll Need to Get COVID-19 Boosters Again and Again (Open access)

 

See more from MedicalBrief archives:

 

FDA authorises Pfizer COVID booster for children aged 5-11

 

Only ‘marginal benefits’ from second COVID booster – Israeli study

 

Warning from WHO and EU regulator against repeat COVID boosters

 

FDA and CDC authorise COVID booster shots for all US adults

 

WHO’s vaccine head on why the rush for COVID booster jabs is premature

 

 

 

 

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