Wikipedia:Reference desk/Archives/Science/2020 March 18

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March 18

Vaccines

• There are very effective vaccines for viruses like smallpox and measles
• There is a new one for each year's seasonal flu, sometimes effective, sometimes less so. Flu keeps mutating so they have to keep reformulating the vaccines.
• There is no vaccine for SARS which is apparently closely related to the SARS-Cov-2 aka Covid-19 that is currently in the news.
• There is also no vaccine for the common cold, though maybe colds are considered only an annoyance and there is too wide a range of viruses causing it for vaccines to target
• There is no HIV vaccine but there has apparently been work in that direction for decades, and there is PreP.
• A vaccine for Ebola was apparently developed at remarkable speed.

Is this all just a matter of chance? Are some kinds of viruses better vaccine targets than others? Why is anyone hopeful about developing a SARS-Cov-2 vaccine anytime soon, given that SARS-Cov-1 has been around so long and there is no vaccine for it? Thanks. 2601:648:8202:96B0:386A:A40C:EBB1:ACC0 (talk) 06:30, 18 March 2020 (UTC)

"SARS-CoV-1 has been around so long" is technically true but IMO too simplistic here. The 2002–2004 SARS outbreak basically ended in 2004, see our article or [1]. AFAIK, there have been no cases since then. This is unlike MERS coronavirus EMC/2012, where an occasional case still happens [2]. (Mostly infection from camels.)

While vaccine development for SARS-CoV-1 didn't completely end then, it and the funding ground down to a trickle [3] [4]. Note that the first source is from 2016, I don't think it's been updated since then. If you look hard enough, I'm sure you'll find plenty of people concerned about the lack of research and the lack of funding before this outbreak, probably especially around the time of the emergency of MERS coronavirus EMC/2012. (Using time based searching will help since of course current results are overwhelmed by results for the pandemic especially since no one called the virus SARS-CoV-1 until recently.) Definitely there are a lot of people saying mistakes were made after SARS-CoV-1 now. Concerns about how medical research is funded, and the attention given to various areas isn't of course unique to that, e.g. new antibiotics to deal with antibiotic resistance or diseases primarily infecting developing countries.

That said, there is a fair amount that goes into vaccine development particularly when the virus has not been targeted. This source [5] outlines one of the concerns relating to vaccines for coronaviruses. There are related issues for the Dengue vaccine. Not completely surprising since it's been recognised for a while that infection with some strain of the Dengue virus by someone who was infected by some other strain is the past can result in a more serious illness.

Nil Einne (talk) 08:24, 18 March 2020 (UTC)

I should add though that funding aside, the final stage of testing your vaccine also falls apart when there's no human population at risk of infection. While human challenges remain a thing, they're generally more regulated than in Edward Jenner's days [6]. And even though useful, I think it's fair to say they don't quite replicate testing your vaccine against a real world spread. Nil Einne (talk) 08:54, 18 March 2020 (UTC)

Is this all just a matter of chance? Are some kinds of viruses better vaccine targets than others? Yes, to some degree. Notably, for HIV, what makes it a pain is that it infects white blood cells, which of course are a core part of the immune system, and suppresses them. Additionally, once it infects them, it "jumps" from cell to cell, which means the virus can "hide" from the immune system. And to add insult to injury, the virus is covered in proteins that "repel" antibodies. Infected people produce antibodies, but these don't neutralize the infection. Since vaccines generally work by stimulating antibody production, this understandably presents a challenge. What a nasty little thing. The common cold is produced by hundreds of different viruses, so an effective "universal" vaccine would have to produce immunity to all these. And of course there's the risk-benefit issue; colds usually aren't serious, so a vaccine would have to have very low incidence of side effects to be acceptable for general use. --47.146.63.87 (talk) 19:08, 18 March 2020 (UTC)

Pollution and convertibles

A while back I heard some research reported on the telly that in city traffic cyclists breathe in less pollution than drivers. The reason given was that cyclists are in the open air whereas drivers are sitting in an enclosed space right behind someone elses exhaust pipe. But I drive a convertible, so top up or top down? Which is healthier? SpinningSpark 08:48, 18 March 2020 (UTC)

While not directly answering the question this [7] may be of interest and maybe also these comments from one of the people involved [8]. And perhaps [9] and these comments from one of the people involved [10] [11] may be of interest. I guess [12] may be of minor interest even if relating to a somewhat different scenario. Nil Einne (talk) 12:16, 18 March 2020 (UTC)

In a steady-state environment, in the long run, unless the inner compartment is completely sealed off (not recommended in a long run), the composition of the inside air will get in equilibrium with that of the outside air. The environment of a car moving in traffic is obviously not in a steady state, but will instead smooth out the fluctuations in the outside environment; the long-term inside and outside average will remain the same. The more closed-off the inside is, the stronger the smoothing effect. If you can control the degree of closure, kind of like Maxwell's demon, you can achieve a better inside average by closing up when the outside is worse than the inside, and opening up otherwise.  --Lambiam 13:29, 18 March 2020 (UTC)

So you are saying I should close the lid when the traffic is queing, but hold everyone up for 30 seconds while I open it again when the traffic moves on? Healthier for pollution, but probably not for incoming road rage. SpinningSpark 13:50, 18 March 2020 (UTC)

Vehicles spuming noxious gases are at their worst when they start moving after having halted, and it takes some time before these gases have wafted off. So I recommend you wait for 30 seconds before you start opening up the roof.  --Lambiam 17:38, 18 March 2020 (UTC)

Try driving behind a bus, a truck, or any old-old vehicle for a while, and you'll get a sense of it. If you're expecting heavy traffic, put the top up and turn on recirculate before you get there. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:50, 18 March 2020 (UTC)

Inside air isn't in equilibrium with the outside, because it's supplied through a filter (for most recent cars). Even for convertibles, the air quality can thus be improved, depending on speed. BMW in particular have worked hard at this. In city traffic though, the low road speed may make the normal air segregation inactive. Andy Dingley (talk) 17:11, 18 March 2020 (UTC)

Such a filter keeps particulate matter (dust, pollen, soot, dirt) out of the cabin, but it offers no barrier against toxic exhaust fumes. For that you'd need an air scrubber.  --Lambiam 17:38, 18 March 2020 (UTC)

But the main pollutant of interest (my country, at least) is particulates from diesels. In particular, the larger particulates from the most poorly maintained of the diesels. Andy Dingley (talk) 18:08, 18 March 2020 (UTC)

Modern vehicles with catalytic converters and fuel injection (and unleaded gasoline) generally produce low levels of "toxic fumes" (volatile organic compounds, carbon monoxide, etc.). Particulate pollution is the nastier stuff. --47.146.63.87 (talk) 19:13, 18 March 2020 (UTC)

to both of the above. From [13]

For a reduction in all traffic-related pollutants, consistent with a sustained 1 µg/m³ reduction of NO
₂, we estimate that about 1.6 million life years could be saved in the UK over the next 106 years, and that life expectancy (at birth) would be increase by around 8 days.

For a 1 µg/m³ reduction in NO
₂ , without a corresponding reduction in concentrations of other traffic-related pollutants, we estimate that about 420,000 to 903,000 life years could be saved in the UK over the next 106 years, and that life expectancy (at birth) would be increased by around 2 to 5 days. We emphasise that these are indicative results because of the need to estimate, using expert judgement, the extent to which observed associations between NO
₂ and mortality are caused by NO
₂ rather than other pollutants.

This suggest particulate pollution is indeed a bigger concern, but by no means sounds nitrogen dioxide from traffic too minor to worry about. It's controversial, there is a dissenting opinion section in that same source. But it seems a better source than what 2 random Wikipedians say without sources.

There is also [14] but the nitrogen dioxide stuff seems to be based on early work that went into that study so it isn't the best source. But this [15] may be of minor interest.

Of course such estimates would I assume also be based in part on the help offered by particulate filters in vehicles and the statistics that many vehicles are not convertibles with their tops down etc. But still, I think we need to be clear on what we're talking about. And plenty of people are affected who are not breathing filtered air in cars etc.

P.S. I maybe should add that although I've heard various comments before including concerns of the consequences of the diesel car boom in Europe, I know little about this. The main reason for my initial scepticism causing me to look into this and find those sources, is because when I was researching my earlier answer, a number of sources including those I did not feel were useful so didn't link above, were talking about the impacts and risks of gases from traffic pollution on people. And they did so in a way which did not suggest they were too minor to worry about.

Nil Einne (talk) 15:30, 19 March 2020 (UTC)

Right, I just meant, in wealthier countries with good emissions controls, particulates are the bigger concern. --47.146.63.87 (talk) 18:32, 19 March 2020 (UTC)

If your car ventilation system has an air filter ("cabin filter") then there might be a HEPA replacement available (e.g: Bosch}. I also cut a carbon filter to fit -- works great. 2606:A000:1126:28D:C16C:DD49:F539:720 (talk) 02:32, 19 March 2020 (UTC)

The thing is, you probably should worry more about being injured in a traffic collision. Reducing risk from that means always leaving the top up. --47.146.63.87 (talk) 18:32, 19 March 2020 (UTC)