The immunologist Viola: «There are no contraindications in changing vaccines: all target the Spike protein». And Moderna triggers increased antibody response
From 1 December all Italians over 18 can receive the third dose of the Covid vaccine after five months. In Italy, regardless of the vaccine used for the first vaccination cycle (AstraZeneca, Moderna, Pfizer, Johnson & Johnson), only one of the two m-Rna vaccines (Pfizer or Moderna) is used as a booster dose. In the case of Moderna, half the dose of the primary vaccination course is sufficient for the booster.
The vaccination campaign
The vaccination campaign on third doses continues fast, but at this end of 2021 Pfizer’s stocks are limited, which is why the third dose is being carried out more often with Moderna which, being administered in half the dose, is also more available. So it will happen that those who have completed the vaccination cycle with Pfizer will likely make the recall with Moderna. And even those under the age of 60 who took the first dose with Astrazeneca and the second with Pfizer (after the problem of thrombosis that emerged with the viral vector preparation) may find themselves doing the third dose with a third vaccine, Moderna in fact. But those who have doubts and prefer Pfizer risk up to a month of waiting.
L’approccio mix and match
Numerous studies conducted in recent months and real-world analyzes have highlighted how the “mix and match” approach is effective and safe and waiting for the “preferred” vaccine is not supported by scientific evidence
. Not only does it show that Moderna has a longer-lasting vaccination efficacy. In immunology it is not uncommon to use different vaccines for boosters. It happened for those against hepatitis B, meningococcus C and for the anti-flu that we repeat every season, as if they were so many calls. The studies conducted so far confirm that the mix is more powerful, with the same safety.
The immunologist of the University of Padua Antonella Viol
a he reassures on Facebook: «There are no problems in changing vaccines because everyone has the Spike protein as a target (antigen) and because many people have already been vaccinated with a heterologous combination of different vaccines. So don’t worry about which vaccine will be used for the booster: whether it is Pfizer or Moderna (half dose) both are fine regardless of what you received during the first vaccination cycle ».
Pfizer and Moderna vaccines are extremely similar: both are made from little balls of fat that carry the same messenger Rna sequence inside the cell: they both produce the exact same Spike protein. “What matters for the immune system is that the Spike protein is produced in both cases: this is our antigen, that is the protein that the immune system must recognize and nothing changes if it arrives with Moderna or Pfizer because you receive the exact same antigen and the same antibodies are formed “explains the immunologist. “It is as if there were a different box, which is then thrown away, but inside the same product”.
The knot of dosages
There is only one between the two mRNA vaccines difference in dosages which affects the effectiveness. Not in initial studies, but in the real world, Moderna has been found to protect better against infection and hospitalization and develop a higher antibody level. While for Pfizer provides 30 micrograms of mRNA at dose with Modern micrograms rise to 100 per dose. For i booster it was decided to keep the same dose for Pfizer, but to halve Moderna (50 micrograms). “Therefore in booster doses, Moderna will have 50 micrograms and Pfizer 30 micrograms and the two preparations are even closer also in terms of dosages: the 20 micrograms more of Moderna may perhaps induce a better activation of the protection, but essentially the two preparations are identical »specifies Antonella Viola.
The “best” call
But what are the reminders (third dose) that most increase immunity against Covid? At the moment only a study just published in the Lancet pushes itself to make an evaluation on booster doses. The research analyzes the efficacy and safety of seven different vaccines (AstraZeneca, Pfizer, Moderna, Johnson & Johnson, Novavax, Valneva, Curevac) for homologous and heterologous boosters. The study, funded by the UK Vaccine Taskforce and the National Institute for Health Research, was conducted on 2,878 adults between the ages of 30 and 78.
All vaccines provoked a strong immune response, although the data varies depending on the combination. However, mRna vaccines appear to induce a greater increase in antibodies and T lymphocytes when given 10-12 weeks after the second dose (regardless of whether the person initially received Pfizer or AstraZeneca). None had any safety concerns, only mild side effects such as fatigue, headache or pain at the injection site. Among the various combinations tested, in the people they had received two doses of AstraZeneca showed a 30-fold increase in antibody levels after a Moderna booster and a 25-fold increase after a Pfizer booster. After two Pfizer doses, which offers higher basic protection than AstraZeneca, the same mRna vaccines performed even better. In detail for those who have had the first Pfizer cycle, Moderna is the third dose that triggers the greatest antibody response with an increase in antibodies of more than ten times (but it should be emphasized that a full dose of Moderna was used in the study while in Italy half a dose was used for the booster).
Double dose
A recent Oxford University study of 1,070 volunteers (which involves the first vaccination course) concluded that combining a first dose of the AstraZeneca vaccine with a second dose of Moderna (or Novavax) results in much higher levels of neutralizing antibodies and T cells compared to two doses of AstraZeneca. Particularly Higher antibodies and T cell responses were induced if the AstraZeneca vaccine was followed by a Moderna vaccine than with two doses of AstraZeneca. The study also found that one dose of the Pfizer vaccine followed by an injection of Moderna was better than two doses of Pfizer.
Side effects
Four vaccine combinations showed an overall increase in reactogenicity (local or systemic adverse reactions): third dose of Moderna (administered as a whole and not half a dose as in Italy) after two of AstraZeneca or Pfizer; third dose AstraZeneca or J&J after Pfizer. Fatigue and pain were the most common reactions, usually within 7 days of the injection. A total of 24 serious adverse events occurred, including 5 in the control group.
T lymphocytes
Are there any differences between Pfizer and Moderna regarding cellular immunity T cell formation? According to a study published in Cell conducted on cancer patients, the differences are minimal: while CD8 lymphocytes (killer lymphocytes that kill virus-infected cells) are stimulated in the same way in the two vaccines, there is a slight advantage with Moderna as regards CD4 lymphocytes (help cells that help the immune system by producing cytokines).
The green light from Ema and Ecdc
Just yesterday Ema (European Medicines Agency) and Ecdc (European Agency for Disease Prevention and Control) published a joint recommendation giving the green light to heterologous vaccination, which is already widely used in Europe and in the world: “The The vaccine mix approach can be used for both the first cycle and boosters. Evidence from heterologous vaccination studies suggests that the combination of vaccines with viral vectors and mRNA vaccines produces good levels of antibodies against Covid 19 virus and a higher T cell response. The heterologous regimens were generally well tolerated“. As for boosters, it is stated that “the evidence available so far with different types of authorized vaccines indicates that a heterologous booster looks good or better in terms of immune responses than a homologous booster. Furthermore, the safety profile of the heterologous and homologous booster combinations remains comparable on the basis of available data “. The benefit of the heterologous recall also translates into more flexibility if there is a problem with the supply or availability of vaccines.
December 8, 2021 (change December 8, 2021 | 18:17)
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