Should you get a COVID-19 booster shot now or wait until the fall? Two immunologists help weigh the options


 Should you get a COVID-19 booster shot now or wait until the fall?  Two immunologists help weigh the options

<span-Klasse="Bildbeschriftung">Clinical studies show that mixing and matching booster vaccines can result in a more robust immune response.</span> <span class="Zuschreibung"><eine Klasse="Verknüpfung " href="" rel="nofollow noopener" Ziel="_leer" data-ylk="slk:SDI Productions/E+ über Getty Images">SDI Productions/E+ via Getty Images</a></span>” src=”–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNTtoPTQ2OA–/ -~B/aD05NTU7dz0xNDQwO2FwcGlkPXl0YWNoeW9u/” data-src=”–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNTtoPTQ2OA –/–~B/aD05NTU7dz0xNDQwO2FwcGlkPXl0YWNoeW9u/″4bef32>e531b/5.e.f73</div>
<p>While COVID-19 vaccines remain highly effective in preventing hospitalizations and deaths, it has become clear that the protection provided by current vaccines is diminishing over time.  This requires the use of booster shots that are safe and effective to boost the immune response against the virus and prolong protection.</p>
<p>But when to get a first or second booster and which shot to choose are open questions.  Many people are unsure whether to wait for new, updated formulations of the COVID-19 vaccines or to mix and match combinations of the original vaccine strains.</p>
<p>SARS-CoV-2, the virus that causes COVID-19, uses its knob-shaped spike protein to enter cells and cause infection.  Each of the existing and upcoming vaccines rely on emulation of the spike protein to trigger the immune response.  However, each vaccine type presents the spike protein to the immune system in a different way.</p>
<p>As immunologists studying inflammatory and infectious diseases, including COVID-19, we are interested in understanding how COVID-19 vaccine designs differ in the type of immunity they elicit and the resulting protection.</p>
<h2>New bivalent vaccines</h2>
<p>Moderna and Pfizer-BioNTech, the two companies whose mRNA vaccines have been the primary options for COVID-19 vaccination in all age groups, both have new vaccine formulations on the way.  A Food and Drug Administration advisory committee is scheduled to meet on June 28, 2022 to review the latest versions and decide which are likely to be recommended for this fall’s booster shots.</p>
<p>Moderna’s new bivalent vaccine mixes mRNA encoding the spike proteins of the original SARS-CoV-2 virus, as well as the slightly different spike protein of the more contagious Omicron variant.</p>
<p>In early June 2022, Moderna said its bivalent vaccine outperformed the original vaccine strain in clinical trials, eliciting a stronger immune response and longer protection against the original SARS-CoV-2 and its variants, including Omicron.</p>
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Moderna later announced that its latest formulation also performs well against the latest Omicron subvariants BA.4 and BA.5, which are fast becoming the dominant strains in the US. Due to the significantly stronger immune response the new shot will elicit, Moderna predicts this protection may last a year and plans to launch its new vaccine in August.

And most recently, on June 25, Pfizer-BioNTech also announced results for its two new COVID-19 vaccine formulations: a bivalent formulation consisting of mRNA coding for the spike proteins of the original SARS-CoV-2 virus. Stem and original BA encoded. 1-omicron subvariant and a “monovalent” version that only targets the spike protein of BA.1.

The company’s preliminary studies showed that both the monovalent and bivalent vaccines elicited antibodies that neutralized the newer omicron BA.4 and BA.5 subvariants, albeit to a lesser extent than the BA.1 subvariant. However, Pfizer’s monovalent vaccine elicited better virus-neutralizing antibodies against the omicron BA.1 subvariant than the bivalent vaccine.

However, whether the differences in the levels of such antibodies observed in the monovalent versus the bivalent vaccines translate into different levels of protection against newer Omicron variants remains to be determined in clinical trials.

Advances in the Novavax vaccine

Another vaccine formulation moving towards approval is Novavax, a vaccine made using the spike protein of the original SARS-CoV-2 virus. The Novavax vaccine has the advantage of being similar to traditional vaccines such as the DTaP vaccines for diphtheria, tetanus and whooping cough or the vaccines for other viral infections such as hepatitis and shingles. The Novavax vaccine has been clinically tested in South Africa, the UK and the US and found to be safe and highly effective with 90% efficacy against mild, moderate and severe forms of COVID-19.

A Food and Drug Administration advisory committee approved the Novavax vaccine in early June 2022. Now the FDA is reviewing the changes Novavax made during the manufacturing process before making its decision to approve the vaccine.

In Australia, the Novavax vaccine has recently been provisionally approved as a booster dose for people aged 18 and over. The company is conducting Phase 3 clinical trials to determine if its vaccine is safe and effective for use as a booster dose in people who have previously received mRNA vaccines.

As these new vaccines become available in the coming months, people will have far more options to mix and match vaccines to improve the duration and quality of their immune protection against COVID-19.

Mix and match

Until then, clinical studies have shown that even mixing and matching existing vaccine types is an effective booster strategy. For example, recent studies suggest that adults who were fully vaccinated with one of the three original COVID-19 vaccines — Pfizer-BioNTech, Moderna, or Johnson & Johnson — were boosted with a different brand of vaccine than the one they had in their received their own vaccine In the first series, they had a similar or more robust immune response compared to being boosted with the same brand of vaccine.

Mixing vaccines has been shown to be safe and effective in various studies. The reason why mixing vaccines might induce a more robust immune response goes back to how each presents the virus’s spike protein to the immune system.

When the SARS-CoV-2 virus mutates in regions of the spike protein, as it has in each of the variants and subvariants, and tries to evade the immune cells, antibodies that recognize different parts of the spike protein can stop it its tracks and prevent the virus from infecting the cells of the body.

Whether you decide to get a booster shot now or wait until the fall, it’s heartening for many to know that more options are on the way.

This article is a re-publication of The Conversation, a non-profit news site dedicated to sharing ideas from academic experts. It was written by: Prakash Nagarkatti, University of South Carolina and Mitzi Nagarkatti, University of South Carolina.

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Prakash Nagarkatti receives financial support from the National Institutes of Health and the National Science Foundation.

Mitzi Nagarkatti receives financial support from the National Institutes of Health

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