After a long time we recently got the really positive news of the Oxford Astra Zeneca vaccine and the Sinovac vaccine showing promising results in the phase I & II trials showing good immune response in human trials. It has been making the rounds of the news cycle. I’m not an expert on vaccines and my core knowledge about vaccines has been from my microbiology textbooks during my medical school. I have of course augmented that knowledge with deeper reading over the years. That of course does not make me an expert to comment on it but I’m putting out my thoughts as an impartial medically trained observer. I argue that vaccines might not be the best answer for managing this pandemic. I’m putting my money on antivirals and other treatment protocols. Hear me out as I make my case and decide if it makes sense.
Vaccines are tough business. From all the decades of collective knowledge in vaccine development we have, it is very rare that we will get a successful vaccine for any disease. Vaccine development takes years and for good reason. It’s not enough to have a working vaccine, it’s efficacy and long term protection it offers is as important if not more. Influenza vaccine has 50-60% efficacy and it is a moving target as the virus mutates every year. Single strand RNA coronaviruses are known to be notorious mutators. Even if we have a working vaccine ready in record time and the SARS-Cov-2 virus doesn’t mutate as much like the other single strand RNA virus- measles, long term protection against Covid-19 is still suspect.
Given that antibodies in those infected are reducing after 2-3 months and reports of re-infection in a few patients 3-4 months after the initial infection we have every reason to doubt the long term sterile immunity like smallpox.
COVID-19 Antibodies Can Disappear After 2-3 Months, Study Shows
“Scientists in China studied 74 people with coronavirus, half symptomatic, half asymptomatic. Eight weeks after recovery, antibody levels fell to undetectable levels in 40% of asymptomatic people.”https://www.medscape.com/viewarticle/932671
The vaccines should be targeting T-cell mediated immunity for long lasting immunity. For that both spike protein and nucleocapsid of the coronavirus needs to be targeted because spike proteins can undergo mutations but nucleocapsid proteins are less likely to. Both the present front-runners vaccines are targeting only the spike proteins. So a second generation vaccine with dual targets as well as a third generation vaccine which could be oral instead of injectable is in the works but may take years to get past the various hurdles.
Covid-19 pandemic: the need for second-generation vaccines
As per computer simulation models, the vaccine needs to be very effective and at least 70-80% of the global population needs to be vaccinated. This is assuming at least a 80% effective vaccine. Tall ask for a world which has not managed universal immunisation for infants let alone adults at this scale. Challenges to adult immunisation and equitable immunisation at low cost is immense. I wonder how we are going to vaccinate 7 Billion humans.
How effective does a COVID-19 coronavirus vaccine need to be to stop the pandemic? A new study has answersHow effective does a COVID-19 coronavirus vaccine need to be to stop the pandemic? A new study has answers
A vaccine that’s 70% effective might not be good enough if too few people are willing to be vaccinated, new research shows.
Vaccine effectiveness and adverse events can vary between different regions and varies demographics globally. Like the oral polio vaccine was less effective in Indian and African populations making eradication difficult in these regions. RSV and HPV vaccines had adverse events in Indian populations. There are population demographics that we cannot give vaccines or is counter productive to. One also has to consider vaccine induced immune enhancement- where the recipient of a vaccine gets a severe form of the disease when infected. It is very rare but not unheard of especially in viral vaccines. Also widespread malnutrition in developing countries make that population poor candidates for vaccinations in general.
We’ve had scientists working on Malaria, Dengue, AIDS, TB etc. for decades without a very effective vaccine. We’ve been lucky in some of course. Small pox, Polio, Measles, Mumps, Rubella, Tetanus, Rabies, Hepatitis A & B, Chicken Pox, Influenza, etc. There are 150+ vaccine candidates but if you read and hear the experts vaccine development, they all say that there is still a chance that none of them may succeed. Success in vaccines are thought to be a moon-shot. Mumps vaccine took 4 years but most take decades.
It’s very rare for a virus to disappear and it is very difficult to achieve it. Smallpox is a big achievement. Polio is close. But we’ve hardly eradicated more than these 2 viruses. People are still getting infected by the 2003 SARS, 2009 H1N1 (Swine Flu), 2014 Ebola virus. Even the Chicken pox virus also doesn’t leave your body once you get it in childhood. It stays in your body’s nerves and causes another severe type of infection called shingles when your body’s immunity is down-many decades later. Even with vaccinations we’ve not eradicated the humble chicken pox virus Varicella Zoster.
Dengue was thought to be a one time infection like chicken pox but now it is well known that there are 4 distinct serotypes with different virulence. So theoretically one can have dengue 4 times with increasing severity-that is if one survives the first 3 episodes. The efforts for a dengue vaccine has been in long in the works. There is a commercially available vaccine since last year but we aren’t sure how good a vaccine it is. There are many candidates and whether any of it will work–we are still to see.
A Review on Dengue Vaccine Development
Dengue virus (DENV) has become a global health threat with about half of the world’s population at risk of infection.A Review on Dengue Vaccine Development – PubMed
Measles, we are seeing a resurgence in many countries now maybe due to the relentless antivaxxers and waning vaccination efforts. The vaccine has more than 90% efficacy and yet worldwide 140,000 children died of it in 2018.
The measles virus was down and out. Now it’s primed for a comeback
More than a decade ago, some experts believed the world was ready to rid itself of measles. Now many fear that a resurgence of cases marks a new normal.The measles virus was down and out. Now it’s primed for a comeback
HIV is a virus that has been worked on like no other virus-nearly 40 years. Maybe soon overtaken by covid. We still don’t have a total cure nor a vaccine. Science with the latest drugs have made a straight death sentence into a chronic disease. That is progress but not a cure.
For a disease which has a high percentage of asymptomatic/mild symptoms subjects, about 15% needing hospitalisation and 2 % fatality, will a vaccine for everybody be better than drugs and treatment protocols which will bring down mortality in the severe cases? I think no. Of course it depends on whether we will be able to come up with better treatments before a working vaccine but from a public health economics perspective, vaccination for such a disease at this scale is not something one can conjure up easily.
To end, I would say that it is good that we’ve found two early front-runners in the race for vaccines. I’m rooting for it too. The point of this thread is that we should moderate our expectations and pursue other ways to mitigate the pandemic.